https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-congruence-theorems/v/triangle-angle-example-1 2023-06-02T19:09:07.369858129Z Triangle exterior angle example An exterior angle is formed outside a triangle by extending a side. Its measure is equal to the sum of the two non-adjacent interior angle measures, thanks to the fact that all angle measures in a triangle add up to 180 degrees. Sal Khan video https://cdn.kastatic.org/googleusercontent/wLp2r0BNUUczDRaf0FEYElR-f16JqkKrGUXqmRV93k5fLjL3OY9okjdUz_do9oPMYQ6F7w7Q2DEqiHXfD9snNWDTPQ Triangle exterior angle example An exterior angle is formed outside a triangle by extending a side. Its measure is equal to the sum of the two non-adjacent interior angle measures, thanks to the fact that all angle measures in a triangle add up to 180 degrees. https://cdn.kastatic.org/ka-youtube-converted/hmj3_zbz2eg.mp4/hmj3_zbz2eg.mp4 363 Triangle angles https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/triangle-angle-example-2 2023-06-02T19:09:07.369858129Z Worked example: Triangle angles (intersecting lines) Learn how to find unknown angles in triangles and intersecting lines. We use concepts like supplementary angles (angles that add up to 180°), vertical angles (opposite angles made by two crossing lines), and exterior angles (angles outside a triangle). There are lots of ways to think about this problem. Sal Khan video https://cdn.kastatic.org/googleusercontent/zGCHqinDWdb7VUFyJHlpvrcCfW_SjkBC1_ufAhF6ZiA9cRZUoXqIwEIpXHI_RdNUYD3l68G9LtVPPZuUkfjUcqA Worked example: Triangle angles (intersecting lines) Learn how to find unknown angles in triangles and intersecting lines. We use concepts like supplementary angles (angles that add up to 180°), vertical angles (opposite angles made by two crossing lines), and exterior angles (angles outside a triangle). There are lots of ways to think about this problem. https://cdn.kastatic.org/ka-youtube-converted/eTwnt4G5xE4.mp4/eTwnt4G5xE4.mp4 295 Triangle angles https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/triangle-angle-example-3 2023-06-02T19:09:07.369858129Z Worked example: Triangle angles (diagram) We have a right triangle that's split into several smaller right triangles. The angle measures in any triangle always add up to 180 degrees. By using this fact and looking at complementary (adding up to 90 degrees) and supplementary (adding up to 180 degrees) angles, we can find the missing angle measures in the triangles. Sal Khan video https://cdn.kastatic.org/googleusercontent/o8ICTuKDwBsQ2PkEj-iWNEdxNrZgClsvpH1n894dLUVrbwhSxxAruyq7FeecsfnfL6j8l0CMmOtP0jkeiMbNvrs Worked example: Triangle angles (diagram) We have a right triangle that's split into several smaller right triangles. The angle measures in any triangle always add up to 180 degrees. By using this fact and looking at complementary (adding up to 90 degrees) and supplementary (adding up to 180 degrees) angles, we can find the missing angle measures in the triangles. https://cdn.kastatic.org/ka-youtube-converted/iqeGTtyzQ1I.mp4/iqeGTtyzQ1I.mp4 342 Triangle angles https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/e/angles_2 2026-03-31T08:44:48.259988263Z Finding angle measures using triangles Use your knowledge about angles to find missing angle measures in various complex situations. David Lai exercise https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/challenging-triangle-angle-problem 2023-06-02T19:09:07.369858129Z Triangle angle challenge problem Learn about the sum of exterior angles in a polygon, specifically a pentagon. We find out that the sum of exterior angles is always the same, no matter the shape of the pentagon. To understand this, we use interior angles and divide the pentagon into triangles. Sal Khan video https://cdn.kastatic.org/googleusercontent/OKCwbZirqxkYi7J87sawZBCWwUgjTOIU0Ml06C_nddO7-hf9QBCZNPBU6hbs2T85baV2XbNeGzw7SrIIgJ42Q-k Triangle angle challenge problem Learn about the sum of exterior angles in a polygon, specifically a pentagon. We find out that the sum of exterior angles is always the same, no matter the shape of the pentagon. To understand this, we use interior angles and divide the pentagon into triangles. https://cdn.kastatic.org/ka-youtube-converted/95logvV8nXY.mp4/95logvV8nXY.mp4 517 Triangle angles https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/v/finding-more-angles 2023-06-02T19:09:07.369858129Z Triangle angle challenge problem 2 Find angle measures in triangles when the given measures are algebraic expressions. The key idea is that the sum of all angles in a triangle is always 180 degrees. We can also use parallel lines and transversals to find angle measures. Sal Khan video https://cdn.kastatic.org/googleusercontent/SVQhkWdZHtQhIhzAJ5GAIj4P77hsA3Zy0xclN-77OmMo60KSWLLH-P4AL5bO2bYznZPehE1BSRBXDuQ28E-_qfFxCg Triangle angle challenge problem 2 Find angle measures in triangles when the given measures are algebraic expressions. The key idea is that the sum of all angles in a triangle is always 180 degrees. We can also use parallel lines and transversals to find angle measures. https://cdn.kastatic.org/ka-youtube-converted/0gzSreH8nUI.mp4/0gzSreH8nUI.mp4 365 Triangle angles