The sum of the angles in a polygon can be found by dividing the polygon into triangles and multiplying the number of triangles by 180º. A formula for this is: (n − 2) × 180º, where n is the number of sides of the polygon.

A pentagon is a five-sided polygon with five angles. The sum of the angles in a pentagon is 540º. The sum of the exterior angles of a pentagon is 360º.

A hexagon is a six-sided polygon with six angles. The sum of the angles in a hexagon is 720º. The sum of the exterior angles of a hexagon is 360º.

An octagon is an eight-sided polygon with eight angles. The sum of the angles in an octagon is 1080º. The sum of the exterior angles of an octagon is 360º.

A decagon is a ten-sided polygon with ten angles. The sum of the angles in an octagon is 1440º. The sum of the exterior angles of a decagon is 360º.

1

State how many sides and angles an octagon has.

2

Sketch a diagram of a regular pentagon of side 10 cm.

3

Calculate the missing values in the given octagon.

4

Sketch a diagram of a regular hexagon of side 8 cm.

5

Calculate the missing angle in the given diagram.