{"appState":{"pageLoadApiCallsStatus":true},"articleState":{"article":{"headers":{"creationTime":"2016-03-26T21:05:32+00:00","modifiedTime":"2016-03-26T21:05:32+00:00","timestamp":"2022-09-14T18:09:40+00:00"},"data":{"breadcrumbs":[{"name":"Academics & The Arts","_links":{"self":"https://dummies-api.dummies.com/v2/categories/33662"},"slug":"academics-the-arts","categoryId":33662},{"name":"Math","_links":{"self":"https://dummies-api.dummies.com/v2/categories/33720"},"slug":"math","categoryId":33720},{"name":"Geometry","_links":{"self":"https://dummies-api.dummies.com/v2/categories/33725"},"slug":"geometry","categoryId":33725}],"title":"Identifying Triangles by Their Angles","strippedTitle":"identifying triangles by their angles","slug":"identifying-triangles-by-their-angles","canonicalUrl":"","seo":{"metaDescription":"You can classify triangles by their angles as well as by their sides. The classifications based on angles are as follows: Acute triangle: A triangle with three ","noIndex":0,"noFollow":0},"content":"<p>You can classify triangles by their angles as well as by their sides. The classifications based on angles are as follows:</p>\n<ul class=\"level-one\">\n <li><p class=\"first-para\"><b>Acute triangle: </b>A triangle with three acute angles (less than 90°).</p>\n </li>\n <li><p class=\"first-para\"><b>Obtuse triangle: </b>A triangle with one obtuse angle (greater than 90°). The other two angles are acute. If a triangle were to have two obtuse angles (or three), two of its sides would go out in opposite directions and never come together to form a triangle.</p>\n </li>\n <li><p class=\"first-para\"><b>Right triangle:</b> A triangle with a single right angle (90°) and two acute angles. The legs of a right triangle are the sides touching the right angle, and the hypotenuse is the side across from the right angle.</p>\n<p class=\"child-para\"><b></b>(For the three types of triangles based on the length of their sides, see the article, “Identifying Scalene, Isosceles, and Equilateral Triangles.”)</p>\n </li>\n</ul>\n<p>The angles of a triangle add up to 180°. That’s another reason why if one of the angles of a triangle is 90° or larger, the other two angles have to be acute.</p>","description":"<p>You can classify triangles by their angles as well as by their sides. The classifications based on angles are as follows:</p>\n<ul class=\"level-one\">\n <li><p class=\"first-para\"><b>Acute triangle: </b>A triangle with three acute angles (less than 90°).</p>\n </li>\n <li><p class=\"first-para\"><b>Obtuse triangle: </b>A triangle with one obtuse angle (greater than 90°). The other two angles are acute. If a triangle were to have two obtuse angles (or three), two of its sides would go out in opposite directions and never come together to form a triangle.</p>\n </li>\n <li><p class=\"first-para\"><b>Right triangle:</b> A triangle with a single right angle (90°) and two acute angles. The legs of a right triangle are the sides touching the right angle, and the hypotenuse is the side across from the right angle.</p>\n<p class=\"child-para\"><b></b>(For the three types of triangles based on the length of their sides, see the article, “Identifying Scalene, Isosceles, and Equilateral Triangles.”)</p>\n </li>\n</ul>\n<p>The angles of a triangle add up to 180°. That’s another reason why if one of the angles of a triangle is 90° or larger, the other two angles have to be acute.</p>","blurb":"","authors":[{"authorId":8957,"name":"Mark Ryan","slug":"mark-ryan","description":" <p><b>Mark Ryan</b> has taught pre-algebra through calculus for more than 25 years. In 1997, he founded The Math Center in Winnetka, Illinois, where he teaches junior high and high school mathematics courses as well as standardized test prep classes. He also does extensive one-on-one tutoring. He is a member of the Authors Guild and the National Council of Teachers of Mathematics. 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Identifying Triangles by Their Angles

By: Mark Ryan and

Updated: 03-26-2016

Geometry For Dummies

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You can classify triangles by their angles as well as by their sides. The classifications based on angles are as follows:

Acute triangle: A triangle with three acute angles (less than 90°).
Obtuse triangle: A triangle with one obtuse angle (greater than 90°). The other two angles are acute. If a triangle were to have two obtuse angles (or three), two of its sides would go out in opposite directions and never come together to form a triangle.
Right triangle: A triangle with a single right angle (90°) and two acute angles. The legs of a right triangle are the sides touching the right angle, and the hypotenuse is the side across from the right angle.

(For the three types of triangles based on the length of their sides, see the article, “Identifying Scalene, Isosceles, and Equilateral Triangles.”)

The angles of a triangle add up to 180°. That’s another reason why if one of the angles of a triangle is 90° or larger, the other two angles have to be acute.

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