The document discusses the Pythagorean theorem, which states that for any right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. It provides the formula a2 + b2 = c2 and examples of using the theorem to find missing side lengths of right triangles. It also asks the reader to determine if a triangle with sides of lengths 8, 15, and 17 is a right triangle using the theorem, and to calculate the diagonal length of a television screen given its width and height.