Theorem. The sum of the interior angles of any triangle is 180°. Here are three proofs for the sum of angles of triangles. Proof 1 uses the fact that the alternate interior angles formed by a transversal with two parallel lines are congruent. Proof 2 uses the exterior angle theorem. Proof 3 uses the idea

This is the third in the series of problems involving transforming polygons into another polygon where the area is preserved. The first is about transforming a shape into another shape of the same area and the second is about transforming a quadrilateral into a triangle of the same area. The following problem builds on the

Quadrilaterals have four sides. To make triangles out of them, three of the vertices should be collinear. Now, what construction should you make so that the area remain unchanged? Here’s how you can transform quadrilaterals into triangles with the same are in three easy steps. 1. Extend one of the sides of the quadrilateral. Let’s