# The Pythagorean theorem

The Pythagorean theorem is a fundamental formula in geometry that relates the length of the sides of a right triangle to the length of the hypotenuse of a right triangle. The figure below is showing how to determine the length of the hypotenuse of a right triangle, C, from the length of the other two sides, A and B, which are perpendicular to each other.

**Figure:** The Pythagorean theorem