In the regular decagon (10-sided polygon) below, find the percentage of the shaded area.

Every other side of a regular decagon is extended to form a regular pentagon, find the ratio of two shaded regions?

A twelve pointed star is made by extending the sides of a regular 12-sided polygon (a dodecagon). What is the measure of the grey angle?

The ratio between the exterior angle and the interior angle of a regular polygon is 2 : 3 . Find the number of sides of the polygon.

Find the area of the shaded region in the following image (We have an isosceles triangle with lengths 10, 10, 12)?