Which geometrical theorem is a fundamental relation in Euclidean geometry involving the longest side of a right-angled triangle?
Hypotenuse: In geometry, a hypotenuse (rarely: "hypothenuse") is the longest side of a right-angled triangle, the side opposite of the right angle. Pythagorean theorem: In mathematics, the Pythagorean theorem, also known as Pythagoras's theorem, is a fundamental relation in Euclidean geometry among the three sides of a right triangle.
Pythagorean theorem