# How do find the perimeter of a triangle?

The easiest way is if you already have the lengths of all three sides of the triangle. In which case, you simply add their lengths together to acquire the perimeter.

However, if you only have the lengths of two sides of a triangle, and it's a right triangle"; you can use the Pythagorean Theorem to determine the length of the third side.

Note: Here are some quick definitions of terms that will be used in the following equations.

A² will represent the height of the triangle.

B² will represent the width of the triangle.

C² will represent the hypotenuse of the triangle.

The "Hypotenuse" is the longest side of a triangle.

A "Right Triangle" is a triangle that has an angle measuring 90°.

When using the Pythagorean Theorem; if you're attempting to find hypotenuse of a triangle; you use the formula "A² + B² = C²". That is; you square the two known sides; then add the products. Upon doing that, find the square root of the sum of both numbers, and you have the length of the hypotenuse.

Upon finding the missing side's length; add the lengths of all three sides, and the resulting number will be the perimeter of the triangle.

If you have the length of one side, and the hypotenuse of a right triangle; and are seeking to find the third side's length; you use the formula "C² - A² = B²" or "C² - B² = A²"; depending on which side your attempting to find the length of.

Like in the previous equation, add the lengths of all three sides together to acquire the perimeter.