The Pythagoras' theorem (or Pythagorean theorem) states that:
"In a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides."
So, if , , and are the three sides of a right-angled triangle and is the longest side (i.e. hypotenuse), then:
The hypotenuse is the longest side of the right triangle and it always exists opposite to the right angle (90° angle) of the triangle. This happens because the side opposite to the greatest angle is the longest.