Chapters

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

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## 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.

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