https://www.khanacademy.org/math/cc-fourth-grade-math/plane-figures/imp-classifying-triangles/v/scalene-isosceles-equilateral-acute-right-obtuse 2023-07-24T13:48:13.07161686Z Classifying triangles The video explores how triangles are classified based on their sides and angles. It introduces the terms scalene, isosceles, and equilateral for side lengths, and acute, right, and obtuse for angles. It emphasizes that triangles can be categorized in multiple ways based on these characteristics. Sal Khan video https://cdn.kastatic.org/googleusercontent/wmcE1ICNQ2GKhtp6LRNQ8JmJgM5inf2NFAG6LfgOiBmBCSF3BfAUk2xVCtag-1XktR-C59FTrWFhayWGscT_vDQy Classifying triangles The video explores how triangles are classified based on their sides and angles. It introduces the terms scalene, isosceles, and equilateral for side lengths, and acute, right, and obtuse for angles. It emphasizes that triangles can be categorized in multiple ways based on these characteristics. https://cdn.kastatic.org/ka-youtube-converted/D5lZ3thuEeA.mp4/D5lZ3thuEeA.mp4 360 Triangles https://www.khanacademy.org/math/geometry/hs-geo-congruence/xff63fac4:hs-geo-congruent-triangles/v/other-triangle-congruence-postulates 2021-07-02T09:35:28Z Triangle congruence postulates/criteria Sal introduces and justifies the SSS, SAS, ASA and AAS postulates for congruent triangles. He also shows that AAA is only good for similarity. For SSA, better to watch next video. Sal Khan video https://cdn.kastatic.org/googleusercontent/0eRO4OWRbVtbriGmo7x79sNd7U-XMRfk7oYDXtdz4Megakos8_IubqGv5NG1xm-jaYrBSJ2-ythdRqyimqwmZlY0iw Triangle congruence postulates/criteria Sal introduces and justifies the SSS, SAS, ASA and AAS postulates for congruent triangles. He also shows that AAA is only good for similarity. For SSA, better to watch next video. https://cdn.kastatic.org/ka-youtube-converted/8Ld8Csu4sEs.mp4/8Ld8Csu4sEs.mp4 808 Triangles https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-triangle-congruence/v/more-on-why-ssa-is-not-a-postulate 2021-07-02T09:35:35Z Why SSA isn't a congruence postulate/criterion There are some cases when SSA can imply triangle congruence, but not always. This is why it's not like the other triangle congruence postulates/criteria. Sal Khan video https://cdn.kastatic.org/googleusercontent/2skaxTFhD7pYHzjlwbm38DhP7E5LjZ0C_3U9QLJ7qxgCszqQ5V9bQJP9eoxK3p3vK3I1w1N2ZWg8WJiD070e16KxJg Why SSA isn't a congruence postulate/criterion There are some cases when SSA can imply triangle congruence, but not always. This is why it's not like the other triangle congruence postulates/criteria. https://cdn.kastatic.org/ka-youtube-converted/f8svAm237xM.mp4/f8svAm237xM.mp4 444 Triangles https://www.khanacademy.org/math/geometry/hs-geo-congruence/xff63fac4:hs-geo-congruent-triangles/v/congruent-triangles-and-sss 2021-07-02T09:35:28Z Corresponding parts of congruent triangles are congruent When two triangles are congruent, we can know that all of their corresponding sides and angles are congruent too! Sal Khan video https://cdn.kastatic.org/googleusercontent/I443_grod2oGBOVt8g2JAMc_UGeH-nCQzdC1ennLrKzo0QPgyly7Ouhpcc4J3Xf7TTQ6XA5MPZemfzmJEVqnfIk5bQ Corresponding parts of congruent triangles are congruent When two triangles are congruent, we can know that all of their corresponding sides and angles are congruent too! https://cdn.kastatic.org/ka-youtube-converted/yp49bc4TT-s.mp4/yp49bc4TT-s.mp4 363 Triangles https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-congruence-theorems/v/proof-sum-of-measures-of-angles-in-a-triangle-are-180 2023-05-12T21:01:01.897246564Z Angles in a triangle sum to 180° proof The sum of the interior angle measures of a triangle always adds up to 180°. We can draw a line parallel to the base of any triangle through its third vertex. Then we use transversals, vertical angles, and corresponding angles to rearrange those angle measures into a straight line, proving that they must add up to 180°. Sal Khan video https://cdn.kastatic.org/googleusercontent/-_9m7sXFJ_DZGRlkqOTzZjy4vuXCY0hC1HrMevIJscQ5fyFoU8mekOV5C99_DXZ89kc-lHRN1rhn4WhPlCY4svU Angles in a triangle sum to 180° proof The sum of the interior angle measures of a triangle always adds up to 180°. We can draw a line parallel to the base of any triangle through its third vertex. Then we use transversals, vertical angles, and corresponding angles to rearrange those angle measures into a straight line, proving that they must add up to 180°. https://cdn.kastatic.org/ka-youtube-converted/6s1CI3uuhko.mp4/6s1CI3uuhko.mp4 268 Triangles 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 Triangles https://www.khanacademy.org/math/revision-up-math-class-6/x362f281d7ea4c7a1:week-3-revision-up-math-class-6/x362f281d7ea4c7a1:triangles-revision-up-class-6-math/e/revision-triangles-up-math-class-6 2026-04-07T22:59:30.107127435Z Revision Triangles Practice problems for revision of Triangles. Satya Swaroop exercise