Pythagoras

Pythagoras was a famous mathematician from a long time ago. He figured out that in a right triangle (a triangle with one angle of 90 degrees), the square of the length of the longest side (called the hypotenuse) is equal to the sum of the squares of the lengths of the other two sides. He wrote this idea down as a rule called the Pythagorean Theorem: a2 + b2 = c2. By using this theorem, you can figure out the length of any side of a right triangle if you know the lengths of the other two sides.