The Pythagorean Theorem
The Pythagorean Theorem applies to right triangles.
a² + b² = c²
The variable c represents the hypotenuse.
Example
If one side is 3 and another side is 4:
3² + 4² = 9 + 16 = 25
c = 5
Historical Note
The theorem is named after the Greek mathematician Pythagoras, although versions were known earlier in other civilizations.