https://www.khanacademy.org/math/cc-fourth-grade-math/plane-figures/imp-angle-introduction/v/acute-right-and-obtuse-angles 2021-06-30T20:49:30Z Acute, right, & obtuse angles Acute angles measure less than 90 degrees.  Right angles measure 90 degrees.  Obtuse angles measure more than 90 degrees.  Learn about angles types and see examples of each. Sal Khan video https://cdn.kastatic.org/googleusercontent/0TrIIisE8BxVp_Bs5Co3G8RXtYcnmx9zu5pR2My5GUcj1JjSm5_G6kkQ4ZMUk0Ln1ry1Q5I7HXnYXTX1BGCdUOnJ Acute, right, & obtuse angles Acute angles measure less than 90 degrees.  Right angles measure 90 degrees.  Obtuse angles measure more than 90 degrees.  Learn about angles types and see examples of each. https://cdn.kastatic.org/ka-youtube-converted/ALhv3Rlydig.mp4/ALhv3Rlydig.mp4 332 Angles https://www.khanacademy.org/math/cc-fourth-grade-math/plane-figures/imp-angle-introduction/e/angle_types 2025-05-27T10:20:27.404259006Z Angle types Determine if an angle is acute, right, or obtuse.  A protractor is provided. Ben Alpert exercise https://www.khanacademy.org/math/cambridge-o-level-mathematics-4024/x3f4c73d082a798eb:geometry/x3f4c73d082a798eb:angles/v/exterior-angle-property 2026-03-10T04:30:37.966653692Z Exterior angle property Created by Khan Academy Khan Academy Pakistan video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Exterior angle property Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/wrf7F5GmzFg.mp4/wrf7F5GmzFg.mp4 263 Angles 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/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 Angles https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-triangle-angles/a/triangle-angles-review 2024-06-17T03:51:36.667583972Z Triangle angles review Review the basics of triangle angles, and then try some practice problems. article 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