GMAT Exam: A Simple Guide To Geometry - Pythagorean Theorem

In a right triangle, the hypotenuse is the side opposite the 90° angle.

Tip: The hypotenuse is always the longest side of the right triangle. The other two sides are the legs.

The Pythagorean theorem tells us that, in a right triangle, c^2 = a^2 + b^2, where c is the length of the hypotenuse and a and b are the lengths of the legs of the right triangle.

For example, use the Pythagorean theorem to find the length, c, of the hypotenuse of the right triangle shown below.


The number 289 has two square roots, 17 and –17.

The negative value is discarded because the length of the hypotenuse (or any side) cannot be negative.