# The diagonal of a rectangle measures 13 centimeters. One side is 12 centimeters long. How do you find the length of the other side?

##### 1 Answer
Oct 16, 2015

The lenght is $5$ cm.

#### Explanation:

Let's say that the $12$-centimeters side is the horizontal one. So, we must find the lenght of the vertical one, which we call $x$.

Notice that the horizontal side, the vertical one and the diagonal form a right triangle, where the catheti are the sides of the rectangle and the hypotenuse is the diagonal. So, using Pythagora's theorem we get

${13}^{2} = {12}^{2} + {x}^{2}$

From which we obtain

$x = \sqrt{{13}^{2} - {12}^{2}} = \sqrt{169 - 144} = \sqrt{25} = 5$.