# Diagonals of a Polygon

A diagonal of a polygon is a line segment that joins two nonconsecutive vertices.

#### Number of Diagonals of a Polygon

4 · (4 − 3) : 2 = **2**

5 · (5 − 3) : 2 = **5** 6 · (6 − 3) : 2 = **9**

#### Diagonal of a Square

By applying the Pythagorean theorem for one of the triangles, we obtain:

#### Example

Calculate the length of the diagonal for the square with a side of 5 cm.

#### Diagonal of a Rectangle

By applying the Pythagorean theorem for one of the triangles, we obtain:

#### Example

Calculate the length of the diagonal of a rectangle of 10 cm base and 6 cm height.

Subject

Site