Learn about the Pythagorean theorem. The Pythagoras theorem is a fundamental relation among the three sides of a right triangle. It is used to determine the missing length of a right triangle. The Pythagoras theorem states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.

Pythagoras theorem can also be used to determine if a triangle is a right triangle or not. The pythagoras ineaquality can be used to determine if a triangle is an acute, right, or obtuse angle. This can be helpful if you are just given the lengths of each side of a triangle rather than trying to graph the triangle.