Pythagoras' Theorem
What is Pythagoras' Theorem?
Trigonometry
Pythagoras' theorem {Review}

Nonrightangled trigonometry

There is a special relationship connecting the side lengths of all rightangled triangles, which is known as Pythagoras' theorem. In any given rightangled triangle, the area of the square formed by the length of the longest side (known as the hypotenuse) is equal to the sum of the squares formed by the lengths of the smaller sides of the triangle.