{"id":4520,"date":"2013-06-29T06:36:23","date_gmt":"2013-06-29T06:36:23","guid":{"rendered":"http:\/\/www.mometrix.com\/academy\/?page_id=4520"},"modified":"2026-03-26T10:03:15","modified_gmt":"2026-03-26T15:03:15","slug":"proof-that-a-triangle-is-180-degrees","status":"publish","type":"page","link":"https:\/\/www.mometrix.com\/academy\/proof-that-a-triangle-is-180-degrees\/","title":{"rendered":"Proof that a Triangle is 180 Degrees"},"content":{"rendered":"\n\t\t\t<div id=\"mmDeferVideoEncompass_5VvPifrms1A\" style=\"position: relative;\">\n\t\t\t<picture>\n\t\t\t\t<source srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.webp\" type=\"image\/webp\">\n\t\t\t\t<source srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.png\" type=\"image\/jpeg\"> \n\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" loading=\"eager\" id=\"videoThumbnailImage_5VvPifrms1A\" data-source-videoID=\"5VvPifrms1A\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/circle-play-duotone.png\" alt=\"Proof that a Triangle is 180 Degrees Video\" height=\"464\" width=\"825\" class=\"size-full\" data-matomo-title = \"Proof that a Triangle is 180 Degrees\">\n\t\t\t<\/picture>\n\t\t\t<\/div>\n\t\t\t<style>img#videoThumbnailImage_5VvPifrms1A:hover {cursor:pointer;} img#videoThumbnailImage_5VvPifrms1A {background-size:contain;background-image:url(\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2023\/01\/1255-proof-that-a-triangle-is-180-degrees-1-1.webp\");}<\/style>\n\t\t\t<script defer>\n\t\t\t  jQuery(\"img#videoThumbnailImage_5VvPifrms1A\").click(function() {\n\t\t\t\tlet videoId = jQuery(this).attr(\"data-source-videoID\");\n\t\t\t\tlet helpTag = '<div id=\"mmDeferVideoYTMessage_5VvPifrms1A\" style=\"display: none;position: absolute;top: -24px;width: 100%;text-align: center;\"><span style=\"font-style: italic;font-size: small;border-top: 1px solid #fc0;\">Having trouble? <a href=\"https:\/\/www.youtube.com\/watch?v='+videoId+'\" target=\"_blank\">Click here to watch on YouTube.<\/a><\/span><\/div>';\n\t\t\t\tlet tag = document.createElement(\"iframe\");\n\t\t\t\ttag.id = \"yt\" + videoId;\n\t\t\t\ttag.src = \"https:\/\/www.youtube-nocookie.com\/embed\/\" + videoId + \"?autoplay=1&controls=1&wmode=opaque&rel=0&egm=0&iv_load_policy=3&hd=0&enablejsapi=1\";\n\t\t\t\ttag.frameborder = 0;\n\t\t\t\ttag.allow = \"autoplay; fullscreen\";\n\t\t\t\ttag.width = this.width;\n\t\t\t\ttag.height = this.height;\n\t\t\t\ttag.setAttribute(\"data-matomo-title\",\"Proof that a Triangle is 180 Degrees\");\n\t\t\t\tjQuery(\"div#mmDeferVideoEncompass_5VvPifrms1A\").html(tag);\n\t\t\t\tjQuery(\"div#mmDeferVideoEncompass_5VvPifrms1A\").prepend(helpTag);\n\t\t\t\tsetTimeout(function(){jQuery(\"div#mmDeferVideoYTMessage_5VvPifrms1A\").css(\"display\", \"block\");}, 2000);\n\t\t\t  });\n\t\t\t  \n\t\t\t<\/script>\n\t\t\n<p><script>\nfunction dvE_Function() {\n  var x = document.getElementById(\"dvE\");\n  if (x.style.display === \"none\") {\n    x.style.display = \"block\";\n  } else {\n    x.style.display = \"none\";\n  }\n}\n<\/script><\/p>\n<div class=\"moc-toc hide-on-desktop hide-on-tablet\">\n<div><button onclick=\"dvE_Function()\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2024\/12\/toc2.svg\" width=\"16\" height=\"16\" alt=\"show or hide table of contents\"><\/button><\/p>\n<p>On this page<\/p>\n<\/div>\n<nav id=\"dvE\" style=\"display:none;\">\n<ul>\n<li class=\"toc-h2\"><a href=\"#How_Many_Degrees_are_in_a_Triangle\" class=\"smooth-scroll\">How Many Degrees are in a Triangle?<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Angles_of_a_Triangle\" class=\"smooth-scroll\">Angles of a Triangle<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Review\" class=\"smooth-scroll\">Review<\/a><\/li>\n<li class=\"toc-h2\"><a href=\"#Frequently_Asked_Questions\" class=\"smooth-scroll\">Frequently Asked Questions<\/a><\/li>\n<\/ul>\n<\/nav>\n<\/div>\n<div class=\"accordion\"><input id=\"transcript\" type=\"checkbox\" class=\"spoiler_button\" \/><label for=\"transcript\">Transcript<\/label><input id=\"FAQs\" type=\"checkbox\" class=\"spoiler_button\" \/><label for=\"FAQs\">FAQs<\/label>\n<div class=\"spoiler\" id=\"transcript-spoiler\">\n<h2><span id=\"How_Many_Degrees_are_in_a_Triangle\" class=\"m-toc-anchor\"><\/span>How Many Degrees are in a Triangle?<\/h2>\n<p>\nOne of the first things we all learned about triangles is that the sum of the interior angles is 180 degrees.<\/p>\n<p>You might have used this knowledge to find the missing <a class=\"ylist\" href=\"https:\/\/www.mometrix.com\/academy\/angles\/\">angle<\/a> in a triangle when you knew the other two, and all was well. But then a seed of doubt or curiosity may have crept in. How do we know that the sum of the angles is always 180? Is there some way that we can definitively prove it? The answer is yes!<\/p>\n<p>To mathematically prove that the angles of a triangle will always add up to 180 degrees, we need to establish some basic facts about angles.<\/p>\n<h2><span id=\"Angles_of_a_Triangle\" class=\"m-toc-anchor\"><\/span>Angles of a Triangle<\/h2>\n<p>\nThe first fact we need to review is the definition of a straight angle.<\/p>\n<p>A <strong>straight angle<\/strong> is just a straight line, which is where it gets its name.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/07\/straight-angle-300x91.png\" alt=\"\" width=\"300\" height=\"91\" class=\"aligncenter size-medium wp-image-84754\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/07\/straight-angle-300x91.png 300w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/07\/straight-angle.png 564w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>We\u2019ve placed three points on it to represent the three angles of a triangle. The straight angle ABC is a 180-degree angle. This will be important later.<\/p>\n<p>To see our next angles, let\u2019s take two straight angles and have another line cross through them:<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-1.png\" alt=\"two parallel lines with one diagonal line intersecting them\" width=\"400\" height=\"294\" class=\"aligncenter size-full wp-image-110874\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-1.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-1-300x221.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>This is what we call a transversal. We can see that there are only two different angle measures when this happens. If we look between the <a class=\"ylist\" href=\"https:\/\/www.mometrix.com\/academy\/parallel-and-perpendicular-lines\/\">parallel lines<\/a>, we can see that the two angles on each side of the transversal line add up to 180 degrees.<\/p>\n<p>This is because the transversal line cuts each of the parallel lines into two pieces. Since the straight line is a straight angle, when it\u2019s cut in half its two halves must add up to the original measure. It\u2019s just like if you cut a meter stick at any point, when you put the two pieces of the stick back together they will still add up to one meter. <\/p>\n<p>If we draw one more line cutting across the parallel lines we can make a triangle.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-2.png\" alt=\"two horizontal parallel lines crossed by two diagonal lines creating a triangle\" width=\"400\" height=\"239\" class=\"aligncenter size-full wp-image-110877\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-2.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-2-300x179.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>Our top group of angles has been changed from a group of four to a group of six because each of the bigger angles has been cut by the new line.<\/p>\n<p>The group of angles on the bottom left is unchanged and there\u2019s a new group of angles created by the new line crossing the bottom parallel line.<\/p>\n<p>Let\u2019s add some angle labels to all the angles between the parallel lines:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-3.png\" alt=\"two horizontal parallel lines crossed by two diagonal lines creating a triangle with angles labeled\" width=\"400\" height=\"238\" class=\"aligncenter size-full wp-image-110883\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-3.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-3-300x179.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>We can see that angles A, B, and C combine to form a straight angle, so that means that their sum must be 180 degrees. Now we can establish that the three angles inside the triangle (B, E &#038; F) also add up to 180. <\/p>\n<p>Angles A and E are <a class=\"ylist\" href=\"https:\/\/www.mometrix.com\/academy\/congruent-angles\/\">congruent angles<\/a>, which means they have the same measure, because they are <strong>alternate interior angles<\/strong> of a transversal with parallel lines. <\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-4.png\" alt=\"triangle with angles A and E labeled\" width=\"400\" height=\"239\" class=\"aligncenter size-full wp-image-110889\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-4.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-4-300x179.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>Angle C and Angle F are congruent for the same reason.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-5.png\" alt=\"triangle with angles C and F labeled\" width=\"400\" height=\"240\" class=\"aligncenter size-full wp-image-110895\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-5.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-5-300x180.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>Angle B happens to be congruent with itself. Therefore, the sum of angles A, B, and C must be equal to the sum of the angles B, E, and F. And since the sum of angles A, B, and C is known to be 180, then the sum of angles B, E, and F must also be 180. Here\u2019s a table that lays everything out for us:<\/p>\n<table class=\"ATable\" style=\"margin: auto; width: 100%; font-size: 90%;\">\n<thead>\n<tr>\n<th><strong>Statement<\/strong><\/th>\n<th><strong>Reason<\/strong><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\\(m \\angle A+m \\angle B+m \\angle C=180 ^{\\circ}\\)<\/td>\n<td>Definition of straight angle<\/td>\n<\/tr>\n<tr>\n<td>\\(m \\angle A+m \\angle E\\)<\/td>\n<td>Alternate interior angles of transversal congruent if parallel lines<\/td>\n<\/tr>\n<tr>\n<td>\\(m \\angle C+m \\angle F\\)<\/td>\n<td>Alternate interior angles of transversal congruent if parallel lines<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\n&nbsp;<br \/>\nThe definition of a straight angle is \u201cThe measure of angle A, plus the measure of angle B, plus the measure of angle C, equals 180 degrees.\u201d \u201cThe measure of angle A equals the measure of angle E\u201d is true because the two angles are congruent, alternate interior angles. The same applies to angles C and F.<\/p>\n<p>Let\u2019s look at it now with the angle measures in place:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-6.png\" alt=\"triangle with all angles labeled in degrees\" width=\"400\" height=\"239\" class=\"aligncenter size-full wp-image-110898\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-6.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-6-300x179.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>When we look at the three angles underneath Line 1, we can see that they add up to 180 degrees just as we know they must. <\/p>\n<p>And the three angles in the triangle have the same three angle measures. This will always be true. If we rotate the line we added and look at the measures again we\u2019ll see that it still works:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-7.png\" alt=\"triangle with all angles labeled in degrees\" width=\"400\" height=\"204\" class=\"aligncenter size-full wp-image-110901\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-7.png 400w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2022\/01\/IMAGE-7-300x153.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>We have 55, 75, and 50 inside the triangle, and 55, 75, and 50 underneath line one. Add these together and you get, surprise, a 180-degree angle.<\/p>\n<hr>\n<h2><span id=\"Review\" class=\"m-toc-anchor\"><\/span>Review<\/h2>\n<p>\nOkay, before we go, let\u2019s go over a couple of quick review questions!<\/p>\n<p>1. What is the measure of a straight angle?<\/p>\n<ol style=\"list-style: upper-alpha;\">\n<li>360\u00b0<\/li>\n<li>180\u00b0<\/li>\n<li>90\u00b0<\/li>\n<li>0\u00b0<\/li>\n<\/ol>\n<div style=\"text-align: center; margin-bottom: 20px;\"><button class=\"buttontranscript\" onClick=\"toggle('Answer1')\">Show Answer<\/button><\/div>\n<div id=\"Answer1\" style=\"display:none; box-shadow: 1.5px 1.5px 5px grey; background-color:#E0E0E0; padding: 30px; padding-bottom: 15px; width: 60%; margin: auto; text-align: center;\">\n<strong>The correct answer is B, 180 degrees!<\/strong><\/p>\n<p style=\"text-align: left;\">\n<\/div>\n<p>\n&nbsp;<\/p>\n<p>\n2. If two angles are alternate interior angles of a transversal with parallel lines, this means that the angles are also<\/p>\n<ol style=\"list-style: upper-alpha;\">\n<li>Congruent<\/li>\n<li>Acute<\/li>\n<li>Noncongruent<\/li>\n<li>Parallel<\/li>\n<\/ol>\n<div style=\"text-align: center; margin-bottom: 20px;\"><button class=\"buttontranscript\" onClick=\"toggle('Answer2')\">Show Answer<\/button><\/div>\n<div id=\"Answer2\" style=\"display:none; box-shadow: 1.5px 1.5px 5px grey; background-color:#E0E0E0; padding: 30px; padding-bottom: 15px; width: 60%; margin: auto; text-align: center;\">\n<strong>The correct answer is A, congruent!<\/strong><\/p>\n<p style=\"text-align: left;\">\n<\/div>\n<p>\n&nbsp;<br \/>\nThat\u2019s all for this review! Thanks for watching, and happy studying! <\/p>\n<ul class=\"citelist\">\n<li><a href=\"https:\/\/www.mathopenref.com\/linearpair.html\"target=\"_blank\">\u201cLinear Pair &#8211; Math Word Definition &#8211; Math Open Reference.\u201d n.d.<\/a><\/li>\n<\/ul>\n<\/div>\n<div class=\"spoiler\" id=\"FAQs-spoiler\">\n<h2 style=\"text-align:center\"><span id=\"Frequently_Asked_Questions\" class=\"m-toc-anchor\"><\/span>Frequently Asked Questions<\/h2>\n<div class=\"faq-list\">\n<div class=\"qa_wrap\">\n<div class=\"q_item text_bold\">\n<h4 class=\"letter\">Q<\/h4>\n<p style=\"line-height: unset;\">How do you prove that a triangle is 180 degrees?<\/p>\n<\/p><\/div>\n<div class=\"a_item\">\n<h4 class=\"letter text_bold\">A<\/h4>\n<p>In a straight angle, such as \\(\u2220A+\u2220B+\u2220C\\) in the red circle, the three angles form 180\u00b0. The transversals created by the side lengths of the triangle form angle pairs that are congruent.<\/p>\n<p>For example, \\(\u2220A\\) and \\(\u2220A\\) are congruent because they are alternate interior angles. \\(\u2220B\\) and \\(\u2220B\\) are also congruent because they are also alternate interior angles. Since \\(\u2220A=\u2220A\\) and \\(\u2220B=\u2220B\\), we know that the interior angles \\(\u2220A+\u2220B+\u2220C\\) must also equal 180\u00b0.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter  wp-image-94492\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/Proof-that-a-triangle-is-180-degrees.png\" alt=\"Proof that a triangle is 180 degrees\" width=\"379.2\" height=\"175.2\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/Proof-that-a-triangle-is-180-degrees.png 1063w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/Proof-that-a-triangle-is-180-degrees-300x139.png 300w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/Proof-that-a-triangle-is-180-degrees-1024x473.png 1024w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/Proof-that-a-triangle-is-180-degrees-768x355.png 768w\" sizes=\"(max-width: 1063px) 100vw, 1063px\" \/><\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div class=\"qa_wrap\">\n<div class=\"q_item text_bold\">\n<h4 class=\"letter\">Q<\/h4>\n<p style=\"line-height: unset;\">Can a triangle be 180 degrees? <\/p>\n<\/p><\/div>\n<div class=\"a_item\">\n<h4 class=\"letter text_bold\">A<\/h4>\n<p>An angle that is 180\u00b0 is considered a straight angle, or essentially a straight line. The interior angles of a triangle need to have a sum of 180\u00b0, which means that none of the angles can individually be 180\u00b0.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div class=\"qa_wrap\">\n<div class=\"q_item text_bold\">\n<h4 class=\"letter\">Q<\/h4>\n<p style=\"line-height: unset;\">Why can&#8217;t a triangle have an 180\u00b0 angle? <\/p>\n<\/p><\/div>\n<div class=\"a_item\">\n<h4 class=\"letter text_bold\">A<\/h4>\n<p>The three interior angles of a triangle will always have a sum of 180\u00b0. A triangle cannot have an individual angle measure of 180\u00b0, because then the other two angles would not exist \\((180\u00b0+0\u00b0+0\u00b0)\\). The three angles of a triangle need to combine to 180\u00b0.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div class=\"qa_wrap\">\n<div class=\"q_item text_bold\">\n<h4 class=\"letter\">Q<\/h4>\n<p style=\"line-height: unset;\">What is the angle sum of a triangle? <\/p>\n<\/p><\/div>\n<div class=\"a_item\">\n<h4 class=\"letter text_bold\">A<\/h4>\n<p>The angle sum of a triangle will always be equal to 180\u00b0. The angle sum of a quadrilateral is equal to 360\u00b0, and a triangle can be created by slicing a quadrilateral in half from corner to corner. Since a triangle is essentially half of a quadrilateral, its angle measures should be half as well. Half of 360\u00b0 is 180\u00b0.<\/p>\n<p>For example, the sum of the angles of the quadrilateral below is 360\u00b0 because it consists of four 90\u00b0 angles. The pink triangle is half of this, therefore the sum of its angle measures should also be half (180\u00b0).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-94489\" src=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/A-quadrilateral-split-in-half-diagonally-to-create-2-triangles-with-angles-45-45-and-90-degrees.png\" alt=\"A quadrilateral split in half diagonally to create 2 triangles with angles 45, 45, and 90 degrees\" width=\"319\" height=\"313\" srcset=\"https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/A-quadrilateral-split-in-half-diagonally-to-create-2-triangles-with-angles-45-45-and-90-degrees.png 677w, https:\/\/www.mometrix.com\/academy\/wp-content\/uploads\/2021\/09\/A-quadrilateral-split-in-half-diagonally-to-create-2-triangles-with-angles-45-45-and-90-degrees-300x295.png 300w\" sizes=\"auto, (max-width: 319px) 100vw, 319px\" \/> <\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div class=\"qa_wrap\">\n<div class=\"q_item text_bold\">\n<h4 class=\"letter\">Q<\/h4>\n<p style=\"line-height: unset;\">What angle equals 180 degrees?<\/p>\n<\/p><\/div>\n<div class=\"a_item\">\n<h4 class=\"letter text_bold\">A<\/h4>\n<p>An angle of 180\u00b0 will always form a straight line. This line is also referred to as a straight angle. One way to prove that a straight angle is 180\u00b0 is to put two right angles together. Two 90\u00b0 angles will form a 180\u00b0 angle, or straight line.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n<div class=\"home-buttons\">\n<p><a href=\"https:\/\/www.mometrix.com\/academy\/geometry\/\">Return to Geometry Videos<\/a><\/p>\n<\/div>\n<p><script>\nfunction toggle(obj) {\n          var obj=document.getElementById(obj);\n          if (obj.style.display == \"block\") obj.style.display = \"none\";\n          else obj.style.display = \"block\";\n}\n<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Return to Geometry Videos<\/p>\n","protected":false},"author":1,"featured_media":100348,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"open","template":"","meta":{"footnotes":""},"class_list":{"0":"post-4520","1":"page","2":"type-page","3":"status-publish","4":"has-post-thumbnail","6":"page_category-math-advertising-group","7":"page_category-triangle-videos","8":"page_type-video","9":"subject_matter-math"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/4520","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/comments?post=4520"}],"version-history":[{"count":7,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/4520\/revisions"}],"predecessor-version":[{"id":260728,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/pages\/4520\/revisions\/260728"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/media\/100348"}],"wp:attachment":[{"href":"https:\/\/www.mometrix.com\/academy\/wp-json\/wp\/v2\/media?parent=4520"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}