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A regular polygon has equal angles and sides. Regular polygons can be inscribed in circles.

## Central Angle of a Regular Polygon The central angle of a regular polygon is formed by two consecutive radius.

If n is the number of sides of a polygon:

Central angle = 360° : n

Central angle of a regular pentagon = 360°: 5 = 72º

## Interior Angle of a Regular Polygon The interior angle of a regular polygon is formed by two consecutive sides.

Interior angle = 180° − central angle

Interior angle of a regular pentagon = 180° − 72° = 108º

## Exterior Angle of a Regular Polygon The exterior angle of a regular polygon is formed by a side and the extension of a consecutive side.

The exterior and interior angles are supplementary, that is to say, that add up 180º.

Exterior angle = central angle

Exterior angle of a regular pentagon = 72º

The perimeter is equal to the sum of the lengths of all sides or the length of a side multiplied by the number of sides.

P = n · l  ## Example

Calculate the perimeter and area of the hexagon:   Need a Maths teacher?

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Emma

I am passionate about travelling and currently live and work in Paris. I like to spend my time reading, gardening, running, learning languages and exploring new places.