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/cc-fourth-grade-math/plane-figures/imp-classifying-triangles/e/recognizing-triangles 2026-03-10T04:30:37.966653692Z Classify triangles by side lengths Practice identifying triangles by their side-lengths as equilateral, isosceles, or scalene. Christopher Wobbles Seymour exercise https://www.khanacademy.org/math/cc-fourth-grade-math/plane-figures/imp-classifying-triangles/e/identifying-triangles-by-angles 2024-04-02T14:40:11.776966208Z Classify triangles by angles Practice identifying triangles by their angles as acute, right, or obtuse. Lindsay exercise https://www.khanacademy.org/math/revision-term-1-mh-math-class-8/x0c43044bb5624863:week-2/x0c43044bb5624863:altitudes-and-median-of-triangles/v/what-are-altitudes-of-triangle 2024-05-28T09:47:20.658952794Z What are altitudes of triangle In this video we discuss what is an altitude of a triangle and how we can draw/identitfy different altitudes of the triangle Devashish Phadnis video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw What are altitudes of triangle In this video we discuss what is an altitude of a triangle and how we can draw/identitfy different altitudes of the triangle https://cdn.kastatic.org/ka-youtube-converted/X2v5aCK5ZoI.mp4/X2v5aCK5ZoI.mp4 206 Triangles https://www.khanacademy.org/districts-courses/geometry-scps-pilot-textbook/x398e4b4a0a333d18:properties-and-attributes-of-triangles/x398e4b4a0a333d18:medians-and-altitudes-of-triangles/v/intro-to-medians-of-a-triangle-class-7-india-math-khan-academy 2021-07-02T09:35:35Z Intro to medians of a triangle Let's get introduced to medians of a triangle and learn what centroids are. Aanand Srinivas video https://cdn.kastatic.org/googleusercontent/t7OPUsgVEIuYj41K54WrfklJHYd53UanJSJy1-buyZqs7XSIOtz2ZajmyOuocKoTtELjjxKf0bqFxqSomwA-11ZNuA Intro to medians of a triangle Let's get introduced to medians of a triangle and learn what centroids are. https://cdn.kastatic.org/ka-youtube-converted/cr92Xwb4CoA.mp4/cr92Xwb4CoA.mp4 328 Triangles https://www.khanacademy.org/districts-courses/geometry-scps-pilot-textbook/x398e4b4a0a333d18:properties-and-attributes-of-triangles/x398e4b4a0a333d18:medians-and-altitudes-of-triangles/e/identify-median-and-altitude 2026-04-08T01:15:04.085520103Z Identify medians and altitudes Practice identifying medians and altitudes in triangles. Ashish exercise 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/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/e/triangle_angles_1 2026-03-31T08:44:48.259988263Z Find angles in triangles Find missing angle measures in triangles using the properties of general triangles, isosceles triangles, and equilateral triangles. Tomer Gal exercise https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-constructing-geometric-shapes/v/triangle-inqequality-theorem 2021-07-02T09:35:27Z Triangle inequality theorem Intuition behind the triangle inequality theorem Sal Khan video https://cdn.kastatic.org/googleusercontent/HVpDfgDPIvUqFIbXtljJrLuUlHyeiWRomrkj6JeKGb5TPNgSbX0u_nX0Aj7RYaPpLreDkNourl80NDiBdD8tPeQ Triangle inequality theorem Intuition behind the triangle inequality theorem https://cdn.kastatic.org/ka-youtube-converted/KlKYvbigBqs.mp4/KlKYvbigBqs.mp4 352 Triangles https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-geometry/cc-7th-constructing-geometric-shapes/e/triangle_inequality_theorem 2025-10-14T14:00:50.911555133Z Triangle side length rules Given the lengths of two sides of a triangle, what can we say about the third side? Igor Terzic exercise https://www.khanacademy.org/math/geometry/hs-geo-congruence/hs-geo-congruence-theorems/v/congruent-legs-and-base-angles-of-isosceles-triangles 2021-02-16T16:08:13Z Proofs concerning isosceles triangles Sal proves that the base angles in isosceles triangles are congruent, and conversely, that triangles with congruent base angles are isosceles. He also proves that the perpendicular to the base of an isosceles triangle bisects it. Sal Khan video https://cdn.kastatic.org/googleusercontent/jEEfJHzFh50C2S_kmU9OCZKaxDbUeLZIoYZkeTy7-8xRyagY_ZkNjJ-ozLt80fhqzLRu8mhn-5yvYZKC43gfD3Xy Proofs concerning isosceles triangles Sal proves that the base angles in isosceles triangles are congruent, and conversely, that triangles with congruent base angles are isosceles. He also proves that the perpendicular to the base of an isosceles triangle bisects it. https://cdn.kastatic.org/ka-youtube-converted/7UISwx2Mr4c.mp4/7UISwx2Mr4c.mp4 543 Triangles https://www.khanacademy.org/math/class-7-ncf/x063f95a40c290960:a-tale-of-three-intersecting-lines/x063f95a40c290960:properties-of-triangles-part-2/v/exterior-angle-property-of-a-triangle 2024-05-28T09:47:20.658952794Z Exterior angle property of a triangle We look at the exterior angle property of the triangle and a quick problem on how to apply it. Devashish Phadnis video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Exterior angle property of a triangle We look at the exterior angle property of the triangle and a quick problem on how to apply it. https://cdn.kastatic.org/ka-youtube-converted/RFKQq6yvRSc.mp4/RFKQq6yvRSc.mp4 263 Triangles https://www.khanacademy.org/math/class-7-ncf/x063f95a40c290960:a-tale-of-three-intersecting-lines/x063f95a40c290960:properties-of-triangles-part-2/e/understand-exterior-angle-property 2026-04-07T23:17:37.123726494Z Understand triangle exterior angle property Let's learn where and how the triangle exterior angle property can be applied. Aanand exercise https://www.khanacademy.org/districts-courses/geometry-scps-pilot-textbook/x398e4b4a0a333d18:triangle-congruence/x398e4b4a0a333d18:angle-relationships-in-triangles/e/exterior-angle-property-problems 2026-04-07T23:36:17.218592739Z Triangle exterior angle property problems Let's use the exterior angle property to find missing angles. Aanand exercise