College Math Placement Practice Test 2026 - Free College Math Questions and Study Guide

The sum of the interior angles of a triangle is 180°. This is a fundamental theorem in geometry. When you add up the angles in any triangle, regardless of its type (scalene, isosceles, or equilateral), you will always find that they total 180°. This property holds true for all triangles and is a result of the fact that the angles of a polygon can be calculated using the formula (n - 2) × 180°, where n is the number of sides. For a triangle, n is 3, so (3 - 2) × 180° equals 180°. Understanding this concept is key to solving many geometry problems involving triangles.