Uploaded January 2016 | Updated September 2026, 2 weeks ago

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This lesson covers angles of a triangle and the triangle sum theorem. Students learn the definition of a triangle, as well as the following triangle classifications: scalene, isosceles, equilateral, acute, obtuse, right, and equiangular. Students also learn the triangle sum theorem, which states that the sum of the measures of the angles of a triangle is 180 degrees. Students are then asked to solve problems related to the triangle sum theorem using Algebra.