{"id":1562,"date":"2021-12-02T19:38:30","date_gmt":"2021-12-03T00:38:30","guid":{"rendered":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/chapter\/11-8-sine-and-cosine-laws\/"},"modified":"2023-08-31T19:29:34","modified_gmt":"2023-08-31T23:29:34","slug":"sine-and-cosine-laws","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/chapter\/sine-and-cosine-laws\/","title":{"raw":"11.8 Sine and Cosine Laws","rendered":"11.8 Sine and Cosine Laws"},"content":{"raw":"Right angle trigonometry is generally limited to triangles that contain a right angle. It is possible to use trigonometry with non-right triangles using two laws: the sine law and the cosine law.\r\n<h1>The Law of Sines<\/h1>\r\nThe sine law is a ratio of sines and opposite sides. The law takes the following form:\r\n\r\n[latex]\\dfrac{a}{\\text{sin }A}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{b}{\\text{sin }B}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{c}{\\text{sin }C}[\/latex]\r\n\r\nSometimes, it is written and used as the reciprocal of the above:\r\n\r\n[latex]\\dfrac{\\text{sin }A}{a}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{\\text{sin }B}{b}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{\\text{sin }C}{c}[\/latex]\r\n\r\n<img class=\"aligncenter wp-image-1538 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1.jpg\" alt=\"The law of sine is used when either 2 sides and 1 opposite angle of 1 of the sides are known, or 2 angles and 1 side of 1 of the angles\" width=\"679\" height=\"187\" \/>\r\n\r\nThe law of sine is used when either two sides and one opposite angle of one of the sides are known, or when there are two angles and one side of one of the angles. If there are two given angles of a triangle, then all three angles are known, since [latex]A^{\\circ} + B^{\\circ} + C^{\\circ} = 180^{\\circ}.[\/latex]\r\n\r\nThe sine law is a very useful law with one caveat in that it is possible to sometimes have two triangles (one larger and one smaller) that generate the same result. This is termed the ambiguous case and is described later in this section.\r\n\r\nThere are also textbook errors where the data given for the triangle is impossible to create. For instance:\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.1<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nCan the following triangle exist?\r\n\r\n<img class=\"aligncenter wp-image-1539 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2.jpg\" alt=\"Triangle with 120, 30 and 30 degree angles, 6 on 2 sides and 10 on the third.\" width=\"759\" height=\"202\" \/>\r\n\r\nIf this triangle can exist, then the ratio of sines for the angles to the opposite sides should equate.\r\n\r\n[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in} = \\hspace{0.25in} \\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in} = \\hspace{0.25in} \\dfrac{10}{\\text{sin }120^{\\circ}}[\/latex]\r\n\r\nReducing this yields:\r\n\r\n[latex]\\dfrac{6}{0.5} \\hspace{0.25in} = \\hspace{0.25in}\\dfrac{6}{0.5} \\hspace{0.25in} = \\hspace{0.25in} \\dfrac{10}{0.866}[\/latex]\r\n\r\nIn checking this out, we find that 12 = 12 \u2260 11.55.\r\n\r\nThis means that this triangle cannot exist.\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.2<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nFind the correct length of the side opposite 120\u00b0 in the triangle shown below.\r\n\r\n<img class=\"aligncenter wp-image-1540 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3.jpg\" alt=\"Triangle with 2-30 degree angles, 1 120 degree. 2 sides with 6 and one side with 10.\" width=\"655\" height=\"208\" \/>\r\n\r\nFor this triangle, the ratio to solve is:\r\n\r\n[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{6}{\\text{sin }30^{\\circ}} \\hspace{0.25in}=\\hspace{0.25in}\\dfrac{x}{\\text{sin }120^{\\circ}} [\/latex]\r\n\r\nWe only need to use one portion of this, so:\r\n\r\n[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{x}{\\text{sin }120^{\\circ}}[\/latex]\r\n\r\nMultiplying both sides of this by sin 120\u00b0, we are left with:\r\n\r\n[latex]x=\\dfrac{6\\text{ sin }120^{\\circ}}{\\text{sin }30^{\\circ}}[\/latex]\r\n\r\nThis leaves us with [latex]x = 10.29[\/latex].\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.3<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nFind the correct length of the side opposite 120\u00b0 in the triangle shown below.\r\n\r\n<img class=\"aligncenter wp-image-1541 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4.jpg\" alt=\"Traingle with 44, 86 and 110 degree sides.\" width=\"605\" height=\"284\" \/>\r\n\r\nFor this triangle, the ratio to solve is:\r\n\r\n[latex]\\dfrac{a}{\\text{sin }44^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{110}{\\text{sin }86^{\\circ}}[\/latex]\r\n\r\nMultiplying both sides by sin 44\u00b0 leaves us with:\r\n\r\n[latex]a=\\dfrac{110\\text{ sin }44^{\\circ}}{\\text{sin }86^{\\circ}}[\/latex]\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.4<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nFind the unknown angle shown in the triangle shown below.\r\n\r\n<img class=\"aligncenter wp-image-1542 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5.jpg\" alt=\"Traingle with 52 degree, 16 and 14 sides\" width=\"489\" height=\"240\" \/>\r\n\r\nFor this triangle, the ratio to solve is:\r\n\r\n[latex]\\dfrac{14}{\\text{sin }A}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{16}{\\text{sin }52^{\\circ}}[\/latex]\r\n\r\nIsolating sin A yields:\r\n\r\n[latex]\\text{sin }A=\\dfrac{14\\text{ sin }52^{\\circ}}{16}[\/latex]\r\n\r\nWe now need to take the inverse sin of both sides to solve for A:\r\n\r\n[latex]\\begin{array}{l}\r\nA=\\text{sin}^{-1}\\left(\\dfrac{14\\text{ sin }52^{\\circ}}{16}\\right) \\\\ \\\\\r\nA=43.6^{\\circ}\r\n\\end{array}[\/latex]\r\n\r\n<\/div>\r\n<\/div>\r\n<h2>The Ambiguous Case<\/h2>\r\nIt is possible, when given the right data, to create two different triangles.\r\n\r\n<img class=\"aligncenter wp-image-1543 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6.jpg\" alt=\"1 triangle with 2 triangles inside. \" width=\"545\" height=\"202\" \/>\r\n\r\nYou can see from the triangle shown above that it is possible to have two angles, B<sub>1<\/sub> and B<sub>2<\/sub>, for side [latex]b[\/latex]. Using the sine law, you will always end up solving for B<sub>1<\/sub>, the angle for the largest triangle. If you are trying to solve for the smaller triangle, then you only need to subtract B<sub>1<\/sub> from 180\u00b0.\r\n\r\nFor example, if B<sub>1<\/sub> = 50\u00b0, then B<sub>2<\/sub> = 180\u00b0 \u2212 B<sub>1<\/sub>. This means B<sub>2<\/sub> = 180\u00b0 \u2212 50\u00b0 or 130\u00b0.\r\n\r\nIf the angle you solve for when using the sine law is smaller than it should be, then correct for it as we just did above.\r\n<h1>The Law of Cosines<\/h1>\r\nThe Law of Cosines is the generalized law of the Pythagorean Theorem [latex](a^2 + b^2 = c^2).[\/latex]\r\n\r\nThe Law of Cosines is generally written in three different forms, which are as follows:\r\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}\r\na^2 = b^2 + c^2 - 2bc\\text{ cos }A \\\\\r\nb^2 = a^2 + c^2 - 2ac\\text{ cos }B \\\\\r\nc^2 = a^2 + b^2 - 2ab\\text{ cos }C\r\n\\end{array}[\/latex]<\/p>\r\nAll forms revert back to one of the three regular forms of the Pythagorean theorem [latex](a^2 = b^2 + c^2, b^2 = a^2 + c^2, c^2 = a^2 + b^2)[\/latex] if [latex]A, B[\/latex] or [latex]C[\/latex] is 90\u00b0, since [latex]\\text{cos }90^{\\circ} = 0.[\/latex] The following examples illustrate the usage of the cosine law in trigonometry\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.5<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nFind the unknown angle shown in the triangle shown below.\r\n\r\n<img class=\"wp-image-1544 size-medium aligncenter\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7-300x282.jpg\" alt=\"Triangle with 100, 90 and 50 sides.\" width=\"300\" height=\"282\" \/>\r\n\r\nFor this triangle:\r\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}\r\nA=\\text{find} \\\\ \\\\\r\na=90 \\\\ \\\\\r\nb=50 \\\\ \\\\\r\nc=100\r\n\\end{array}[\/latex]<\/p>\r\nNote that [latex]b[\/latex] and [latex]c[\/latex] could be switched around. Now, to solve:\r\n<p style=\"text-align: center;\">[latex]\\begin{array}{rrlllll}\r\na^2 &amp;= &amp;\\phantom{-}b^2 &amp;+ &amp;c^2 &amp;-&amp; 2bc\\text{ cos }A \\\\ \\\\\r\n90^2 &amp;= &amp;\\phantom{-}50^2 &amp;+ &amp;100^2 &amp;- &amp;2(50)(100)\\text{ cos } A \\\\\r\n8100&amp; =&amp;\\phantom{-}2500 &amp;+ &amp;10000&amp; - &amp;10000\\text{ cos }A \\\\\r\n-2500&amp;&amp;-2500&amp;-&amp;10000&amp;&amp; \\\\\r\n\\hline\r\n-4400&amp; =&amp;-10000&amp;\\text{ cos }&amp;A&amp;&amp; \\\\ \\\\\r\n\\text{ cos }A&amp; =&amp;\\dfrac{-4400}{-10000}&amp;&amp;&amp;&amp; \\\\ \\\\\r\nB&amp; =&amp;\\text{cos}^{-1}0.44&amp;&amp;&amp;&amp; \\\\ \\\\\r\nB&amp;=&amp;63.9^{\\circ}&amp;&amp;&amp;&amp;\r\n\\end{array}[\/latex]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example 11.8.6<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nFind the unknown side shown in the triangle shown below.\r\n\r\n<img class=\"wp-image-1545 size-medium aligncenter\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-300x284.jpg\" alt=\"Triangle with sides of 96 and 60, and an angle of 70 degrees\" width=\"300\" height=\"284\" \/>For this triangle:\r\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}\r\nB=70^{\\circ} \\\\ \\\\\r\na=95 \\\\ \\\\\r\nb=\\text{find} \\\\ \\\\\r\nc=60\r\n\\end{array}[\/latex]<\/p>\r\nNote that [latex]b[\/latex] and [latex]c[\/latex] could be switched around. Now, to solve:\r\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}\r\nb^2=a^2+c^2-2ac\\text{ cos }B \\\\ \\\\\r\nb^2=95^2+60^2-2(95)(60)\\text{ cos }70^{\\circ} \\\\\r\nb^2=9025+3600-11400(0.34202) \\\\\r\nb^2=12625 - 3899 \\\\\r\nb^2=8726 \\\\ \\\\\r\nb=\\sqrt{8726} \\\\\r\nb=93.4\r\n\\end{array}[\/latex]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\nUnlike with the law of sines, there should be no ambiguous cases with the law of cosines.\r\n<h1>Questions<\/h1>\r\nSolve all unknowns in the following non-right triangles using either the law of sines or cosines.\r\n<ol class=\"twocolumn\">\r\n \t<li><img class=\"alignnone wp-image-1546 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question1-e1646951614742.jpg\" alt=\"Traingle with sides 10 and 20, angle between is 40 degrees.\" width=\"289\" height=\"141\" \/><\/li>\r\n \t<li><img class=\"alignnone size-full wp-image-1547\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question2.jpg\" alt=\"Triangle with sides of 28, 28 and 20\" width=\"251\" height=\"255\" \/><\/li>\r\n \t<li><img class=\"alignnone size-medium wp-image-1548\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3-300x150.jpg\" alt=\"Triangle with sides 200, 140 and 130\" width=\"300\" height=\"150\" \/><\/li>\r\n \t<li><img class=\"alignnone size-full wp-image-1549\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question4.jpg\" alt=\"Triangle with sides 125, 120 and angle between of 32 degrees\" width=\"219\" height=\"253\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1550 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question5.jpg\" alt=\"Traingle with sides 18, 20 and 3\" width=\"127\" height=\"231\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1551 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question6-e1646952268882.jpg\" alt=\"Traingle with 65 degrees, 35 degrees and side of 40\" width=\"300\" height=\"270\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1552 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question7-e1646952298137.jpg\" alt=\"Triangle with angles of 25 and 28 degrees, side of 12\" width=\"255\" height=\"194\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1553 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862.jpg\" alt=\"Triangle with angles of 15 and 25 degrees, side of 10\" width=\"307\" height=\"137\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1554 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question9-e1646952602840.jpg\" alt=\"Traingle with angles of 10 and 70 degrees, and a side of 8 cm\" width=\"162\" height=\"250\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1555 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375.jpg\" alt=\"Triangle with sides of 28 and 20 cm, angle between of 130 degrees\" width=\"332\" height=\"110\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1556 size-medium\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11-300x204.jpg\" alt=\"Triangle with sides of 30, 20 and 15 m\" width=\"300\" height=\"204\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1557 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question12-e1646952635466.jpg\" alt=\"Triangle with angles of 95 and 20 degrees, side of 8 m\" width=\"268\" height=\"140\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1558 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question13.jpg\" alt=\"Triangle with sides of 10, 16 and 8 cm\" width=\"300\" height=\"182\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1559 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441.jpg\" alt=\"Triangle with sides of 20 and 24 cm, 15 degree angle\" width=\"327\" height=\"132\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1560 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question15.jpg\" alt=\"Triangle with sides of 22, 20 and 10 m\" width=\"250\" height=\"241\" \/><\/li>\r\n \t<li><img class=\"alignnone wp-image-1561 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question16-e1646952686599.jpg\" alt=\"Triangle with angles of 28 and 25 degrees, 20 m side\" width=\"270\" height=\"182\" \/><\/li>\r\n<\/ol>\r\n<a class=\"internal\" href=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/back-matter\/answer-key-11-8\/\">Answer Key 11.8<\/a>","rendered":"<p>Right angle trigonometry is generally limited to triangles that contain a right angle. It is possible to use trigonometry with non-right triangles using two laws: the sine law and the cosine law.<\/p>\n<h1>The Law of Sines<\/h1>\n<p>The sine law is a ratio of sines and opposite sides. The law takes the following form:<\/p>\n<p>[latex]\\dfrac{a}{\\text{sin }A}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{b}{\\text{sin }B}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{c}{\\text{sin }C}[\/latex]<\/p>\n<p>Sometimes, it is written and used as the reciprocal of the above:<\/p>\n<p>[latex]\\dfrac{\\text{sin }A}{a}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{\\text{sin }B}{b}\\hspace{0.25in} =\\hspace{0.25in} \\dfrac{\\text{sin }C}{c}[\/latex]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1538 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1.jpg\" alt=\"The law of sine is used when either 2 sides and 1 opposite angle of 1 of the sides are known, or 2 angles and 1 side of 1 of the angles\" width=\"679\" height=\"187\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1.jpg 679w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1-300x83.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1-65x18.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1-225x62.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2021\/12\/chapter-11.8_image-1-350x96.jpg 350w\" sizes=\"auto, (max-width: 679px) 100vw, 679px\" \/><\/p>\n<p>The law of sine is used when either two sides and one opposite angle of one of the sides are known, or when there are two angles and one side of one of the angles. If there are two given angles of a triangle, then all three angles are known, since [latex]A^{\\circ} + B^{\\circ} + C^{\\circ} = 180^{\\circ}.[\/latex]<\/p>\n<p>The sine law is a very useful law with one caveat in that it is possible to sometimes have two triangles (one larger and one smaller) that generate the same result. This is termed the ambiguous case and is described later in this section.<\/p>\n<p>There are also textbook errors where the data given for the triangle is impossible to create. For instance:<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.1<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Can the following triangle exist?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1539 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2.jpg\" alt=\"Triangle with 120, 30 and 30 degree angles, 6 on 2 sides and 10 on the third.\" width=\"759\" height=\"202\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2.jpg 759w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2-300x80.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2-65x17.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2-225x60.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-2-350x93.jpg 350w\" sizes=\"auto, (max-width: 759px) 100vw, 759px\" \/><\/p>\n<p>If this triangle can exist, then the ratio of sines for the angles to the opposite sides should equate.<\/p>\n<p>[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in} = \\hspace{0.25in} \\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in} = \\hspace{0.25in} \\dfrac{10}{\\text{sin }120^{\\circ}}[\/latex]<\/p>\n<p>Reducing this yields:<\/p>\n<p>[latex]\\dfrac{6}{0.5} \\hspace{0.25in} = \\hspace{0.25in}\\dfrac{6}{0.5} \\hspace{0.25in} = \\hspace{0.25in} \\dfrac{10}{0.866}[\/latex]<\/p>\n<p>In checking this out, we find that 12 = 12 \u2260 11.55.<\/p>\n<p>This means that this triangle cannot exist.<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.2<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Find the correct length of the side opposite 120\u00b0 in the triangle shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1540 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3.jpg\" alt=\"Triangle with 2-30 degree angles, 1 120 degree. 2 sides with 6 and one side with 10.\" width=\"655\" height=\"208\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3.jpg 655w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3-300x95.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3-65x21.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3-225x71.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-3-350x111.jpg 350w\" sizes=\"auto, (max-width: 655px) 100vw, 655px\" \/><\/p>\n<p>For this triangle, the ratio to solve is:<\/p>\n<p>[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{6}{\\text{sin }30^{\\circ}} \\hspace{0.25in}=\\hspace{0.25in}\\dfrac{x}{\\text{sin }120^{\\circ}}[\/latex]<\/p>\n<p>We only need to use one portion of this, so:<\/p>\n<p>[latex]\\dfrac{6}{\\text{sin }30^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{x}{\\text{sin }120^{\\circ}}[\/latex]<\/p>\n<p>Multiplying both sides of this by sin 120\u00b0, we are left with:<\/p>\n<p>[latex]x=\\dfrac{6\\text{ sin }120^{\\circ}}{\\text{sin }30^{\\circ}}[\/latex]<\/p>\n<p>This leaves us with [latex]x = 10.29[\/latex].<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.3<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Find the correct length of the side opposite 120\u00b0 in the triangle shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1541 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4.jpg\" alt=\"Traingle with 44, 86 and 110 degree sides.\" width=\"605\" height=\"284\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4.jpg 605w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4-300x141.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4-65x31.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4-225x106.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-4-350x164.jpg 350w\" sizes=\"auto, (max-width: 605px) 100vw, 605px\" \/><\/p>\n<p>For this triangle, the ratio to solve is:<\/p>\n<p>[latex]\\dfrac{a}{\\text{sin }44^{\\circ}}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{110}{\\text{sin }86^{\\circ}}[\/latex]<\/p>\n<p>Multiplying both sides by sin 44\u00b0 leaves us with:<\/p>\n<p>[latex]a=\\dfrac{110\\text{ sin }44^{\\circ}}{\\text{sin }86^{\\circ}}[\/latex]<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.4<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Find the unknown angle shown in the triangle shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1542 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5.jpg\" alt=\"Traingle with 52 degree, 16 and 14 sides\" width=\"489\" height=\"240\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5.jpg 489w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5-300x147.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5-65x32.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5-225x110.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-5-350x172.jpg 350w\" sizes=\"auto, (max-width: 489px) 100vw, 489px\" \/><\/p>\n<p>For this triangle, the ratio to solve is:<\/p>\n<p>[latex]\\dfrac{14}{\\text{sin }A}\\hspace{0.25in}=\\hspace{0.25in}\\dfrac{16}{\\text{sin }52^{\\circ}}[\/latex]<\/p>\n<p>Isolating sin A yields:<\/p>\n<p>[latex]\\text{sin }A=\\dfrac{14\\text{ sin }52^{\\circ}}{16}[\/latex]<\/p>\n<p>We now need to take the inverse sin of both sides to solve for A:<\/p>\n<p>[latex]\\begin{array}{l}  A=\\text{sin}^{-1}\\left(\\dfrac{14\\text{ sin }52^{\\circ}}{16}\\right) \\\\ \\\\  A=43.6^{\\circ}  \\end{array}[\/latex]<\/p>\n<\/div>\n<\/div>\n<h2>The Ambiguous Case<\/h2>\n<p>It is possible, when given the right data, to create two different triangles.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1543 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6.jpg\" alt=\"1 triangle with 2 triangles inside.\" width=\"545\" height=\"202\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6.jpg 545w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6-300x111.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6-65x24.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6-225x83.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-6-350x130.jpg 350w\" sizes=\"auto, (max-width: 545px) 100vw, 545px\" \/><\/p>\n<p>You can see from the triangle shown above that it is possible to have two angles, B<sub>1<\/sub> and B<sub>2<\/sub>, for side [latex]b[\/latex]. Using the sine law, you will always end up solving for B<sub>1<\/sub>, the angle for the largest triangle. If you are trying to solve for the smaller triangle, then you only need to subtract B<sub>1<\/sub> from 180\u00b0.<\/p>\n<p>For example, if B<sub>1<\/sub> = 50\u00b0, then B<sub>2<\/sub> = 180\u00b0 \u2212 B<sub>1<\/sub>. This means B<sub>2<\/sub> = 180\u00b0 \u2212 50\u00b0 or 130\u00b0.<\/p>\n<p>If the angle you solve for when using the sine law is smaller than it should be, then correct for it as we just did above.<\/p>\n<h1>The Law of Cosines<\/h1>\n<p>The Law of Cosines is the generalized law of the Pythagorean Theorem [latex](a^2 + b^2 = c^2).[\/latex]<\/p>\n<p>The Law of Cosines is generally written in three different forms, which are as follows:<\/p>\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}  a^2 = b^2 + c^2 - 2bc\\text{ cos }A \\\\  b^2 = a^2 + c^2 - 2ac\\text{ cos }B \\\\  c^2 = a^2 + b^2 - 2ab\\text{ cos }C  \\end{array}[\/latex]<\/p>\n<p>All forms revert back to one of the three regular forms of the Pythagorean theorem [latex](a^2 = b^2 + c^2, b^2 = a^2 + c^2, c^2 = a^2 + b^2)[\/latex] if [latex]A, B[\/latex] or [latex]C[\/latex] is 90\u00b0, since [latex]\\text{cos }90^{\\circ} = 0.[\/latex] The following examples illustrate the usage of the cosine law in trigonometry<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.5<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Find the unknown angle shown in the triangle shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1544 size-medium aligncenter\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7-300x282.jpg\" alt=\"Triangle with 100, 90 and 50 sides.\" width=\"300\" height=\"282\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7-300x282.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7-65x61.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7-225x212.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-7.jpg 318w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>For this triangle:<\/p>\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}  A=\\text{find} \\\\ \\\\  a=90 \\\\ \\\\  b=50 \\\\ \\\\  c=100  \\end{array}[\/latex]<\/p>\n<p>Note that [latex]b[\/latex] and [latex]c[\/latex] could be switched around. Now, to solve:<\/p>\n<p style=\"text-align: center;\">[latex]\\begin{array}{rrlllll}  a^2 &= &\\phantom{-}b^2 &+ &c^2 &-& 2bc\\text{ cos }A \\\\ \\\\  90^2 &= &\\phantom{-}50^2 &+ &100^2 &- &2(50)(100)\\text{ cos } A \\\\  8100& =&\\phantom{-}2500 &+ &10000& - &10000\\text{ cos }A \\\\  -2500&&-2500&-&10000&& \\\\  \\hline  -4400& =&-10000&\\text{ cos }&A&& \\\\ \\\\  \\text{ cos }A& =&\\dfrac{-4400}{-10000}&&&& \\\\ \\\\  B& =&\\text{cos}^{-1}0.44&&&& \\\\ \\\\  B&=&63.9^{\\circ}&&&&  \\end{array}[\/latex]<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 11.8.6<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Find the unknown side shown in the triangle shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1545 size-medium aligncenter\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-300x284.jpg\" alt=\"Triangle with sides of 96 and 60, and an angle of 70 degrees\" width=\"300\" height=\"284\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-300x284.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-65x61.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-225x213.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8-350x331.jpg 350w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_image-8.jpg 366w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/>For this triangle:<\/p>\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}  B=70^{\\circ} \\\\ \\\\  a=95 \\\\ \\\\  b=\\text{find} \\\\ \\\\  c=60  \\end{array}[\/latex]<\/p>\n<p>Note that [latex]b[\/latex] and [latex]c[\/latex] could be switched around. Now, to solve:<\/p>\n<p style=\"text-align: center;\">[latex]\\begin{array}{l}  b^2=a^2+c^2-2ac\\text{ cos }B \\\\ \\\\  b^2=95^2+60^2-2(95)(60)\\text{ cos }70^{\\circ} \\\\  b^2=9025+3600-11400(0.34202) \\\\  b^2=12625 - 3899 \\\\  b^2=8726 \\\\ \\\\  b=\\sqrt{8726} \\\\  b=93.4  \\end{array}[\/latex]<\/p>\n<\/div>\n<\/div>\n<p>Unlike with the law of sines, there should be no ambiguous cases with the law of cosines.<\/p>\n<h1>Questions<\/h1>\n<p>Solve all unknowns in the following non-right triangles using either the law of sines or cosines.<\/p>\n<ol class=\"twocolumn\">\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1546 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question1-e1646951614742.jpg\" alt=\"Traingle with sides 10 and 20, angle between is 40 degrees.\" width=\"289\" height=\"141\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question1-e1646951614742.jpg 289w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question1-e1646951614742-65x32.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question1-e1646951614742-225x110.jpg 225w\" sizes=\"auto, (max-width: 289px) 100vw, 289px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1547\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question2.jpg\" alt=\"Triangle with sides of 28, 28 and 20\" width=\"251\" height=\"255\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question2.jpg 251w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question2-65x66.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question2-225x229.jpg 225w\" sizes=\"auto, (max-width: 251px) 100vw, 251px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-1548\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3-300x150.jpg\" alt=\"Triangle with sides 200, 140 and 130\" width=\"300\" height=\"150\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3-300x150.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3-65x33.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3-225x113.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question3.jpg 307w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1549\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question4.jpg\" alt=\"Triangle with sides 125, 120 and angle between of 32 degrees\" width=\"219\" height=\"253\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question4.jpg 219w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question4-65x75.jpg 65w\" sizes=\"auto, (max-width: 219px) 100vw, 219px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1550 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question5.jpg\" alt=\"Traingle with sides 18, 20 and 3\" width=\"127\" height=\"231\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question5.jpg 127w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question5-65x118.jpg 65w\" sizes=\"auto, (max-width: 127px) 100vw, 127px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1551 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question6-e1646952268882.jpg\" alt=\"Traingle with 65 degrees, 35 degrees and side of 40\" width=\"300\" height=\"270\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question6-e1646952268882.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question6-e1646952268882-65x59.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question6-e1646952268882-225x203.jpg 225w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1552 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question7-e1646952298137.jpg\" alt=\"Triangle with angles of 25 and 28 degrees, side of 12\" width=\"255\" height=\"194\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question7-e1646952298137.jpg 255w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question7-e1646952298137-65x49.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question7-e1646952298137-225x171.jpg 225w\" sizes=\"auto, (max-width: 255px) 100vw, 255px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1553 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862.jpg\" alt=\"Triangle with angles of 15 and 25 degrees, side of 10\" width=\"307\" height=\"137\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862.jpg 307w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862-300x134.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862-65x29.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question8-e1646952314862-225x100.jpg 225w\" sizes=\"auto, (max-width: 307px) 100vw, 307px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1554 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question9-e1646952602840.jpg\" alt=\"Traingle with angles of 10 and 70 degrees, and a side of 8 cm\" width=\"162\" height=\"250\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question9-e1646952602840.jpg 162w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question9-e1646952602840-65x100.jpg 65w\" sizes=\"auto, (max-width: 162px) 100vw, 162px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1555 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375.jpg\" alt=\"Triangle with sides of 28 and 20 cm, angle between of 130 degrees\" width=\"332\" height=\"110\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375.jpg 332w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375-300x99.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375-65x22.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question10-e1646952538375-225x75.jpg 225w\" sizes=\"auto, (max-width: 332px) 100vw, 332px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1556 size-medium\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11-300x204.jpg\" alt=\"Triangle with sides of 30, 20 and 15 m\" width=\"300\" height=\"204\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11-300x204.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11-65x44.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11-225x153.jpg 225w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question11.jpg 305w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1557 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question12-e1646952635466.jpg\" alt=\"Triangle with angles of 95 and 20 degrees, side of 8 m\" width=\"268\" height=\"140\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question12-e1646952635466.jpg 268w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question12-e1646952635466-65x34.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question12-e1646952635466-225x118.jpg 225w\" sizes=\"auto, (max-width: 268px) 100vw, 268px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1558 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question13.jpg\" alt=\"Triangle with sides of 10, 16 and 8 cm\" width=\"300\" height=\"182\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question13.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question13-65x39.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question13-225x137.jpg 225w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1559 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441.jpg\" alt=\"Triangle with sides of 20 and 24 cm, 15 degree angle\" width=\"327\" height=\"132\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441.jpg 327w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441-300x121.jpg 300w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441-65x26.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question14-1-e1646952660441-225x91.jpg 225w\" sizes=\"auto, (max-width: 327px) 100vw, 327px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1560 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question15.jpg\" alt=\"Triangle with sides of 22, 20 and 10 m\" width=\"250\" height=\"241\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question15.jpg 250w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question15-65x63.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/11.8_question15-225x217.jpg 225w\" sizes=\"auto, (max-width: 250px) 100vw, 250px\" \/><\/li>\n<li><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1561 size-full\" src=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question16-e1646952686599.jpg\" alt=\"Triangle with angles of 28 and 25 degrees, 20 m side\" width=\"270\" height=\"182\" srcset=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question16-e1646952686599.jpg 270w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question16-e1646952686599-65x44.jpg 65w, https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-content\/uploads\/sites\/304\/2022\/11\/chapter-11.8_question16-e1646952686599-225x152.jpg 225w\" sizes=\"auto, (max-width: 270px) 100vw, 270px\" \/><\/li>\n<\/ol>\n<p><a class=\"internal\" href=\"https:\/\/opentextbc.ca\/intermediatealgebraberg\/back-matter\/answer-key-11-8\/\">Answer Key 11.8<\/a><\/p>\n","protected":false},"author":90,"menu_order":8,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[],"license":[56],"class_list":["post-1562","chapter","type-chapter","status-publish","hentry","license-cc-by-nc-sa"],"part":1491,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapters\/1562","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/wp\/v2\/users\/90"}],"version-history":[{"count":2,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapters\/1562\/revisions"}],"predecessor-version":[{"id":2180,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapters\/1562\/revisions\/2180"}],"part":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/parts\/1491"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapters\/1562\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/wp\/v2\/media?parent=1562"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/pressbooks\/v2\/chapter-type?post=1562"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/wp\/v2\/contributor?post=1562"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/intermediatealgebraberg\/wp-json\/wp\/v2\/license?post=1562"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}