This document discusses the Pythagorean theorem. It contains the following key points: 1. The Pythagorean theorem states that for a right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. The hypotenuse is always opposite the right angle. 2. The theorem can be used to find the length of an unknown side of a right triangle if the lengths of the other two sides are given. 3. Examples are provided to demonstrate using the Pythagorean theorem to calculate missing side lengths of right triangles.