The document discusses the Pythagorean theorem and distance formula. The Pythagorean theorem 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 an example of using the theorem to solve for the length of one side of a right triangle given the other two sides. The distance formula is also introduced as a way to calculate the distance between any two points by using their x- and y-coordinates.