# What is the length of a diagonal of a rectangle whose sides are 5cm and 12cm long?

A rectangle is a four-sided polygon with opposite pairs of sides congruent and all angles measure 90º.

## Answer: The length of a diagonal of a rectangle whose sides are 5 cm and 12 cm long is 13 cm.

Let's find the length of the diagonal step by step.

**Explanation:**

Let ABCD be the rectangle.

In the above triangle ABCD, the diagonal AC divides the rectangle in two right angled triangles △ ABC and △ ADC.

Given In △ ABC,

AB = 12 cm, BC = 5 cm and AC = ?

By applying Pythagorean theorem of right triangle,

⇒ AC^{2} = AB^{2} + BC^{2}

⇒ AC^{2} = (12 cm)^{2} + (5 cm)^{2}

⇒ AC^{2} = 144 + 25

⇒ AC^{2} = 169

⇒ AC = √169

⇒ AC = 13 cm