B. The Pythagorean Theorem

The Pythagorean theorem can be used to find an unknown side length of a right triangle when the other two side lengths are known.

  • Side c represents the longest side of the triangle, also known as the hypotenuse. Side c is also the side opposite the right angle. The longest side of a right triangle is always opposite the right angle.

  • Sides a and b are the legs of the right triangle.

Example 1

Determine the length of side s, to the nearest tenth of a centimetre.

Use the Pythagorean theorem.

Since s is the longest side, the formula can be rewritten with s as the hypotenuse.


 

Example 2

Determine the length of side h, to the nearest tenth of a metre.

Use the Pythagorean theorem.

Since h is one of the legs of the triangle, the formula can be rewritten as follows: