Five

There are various pentagon in the nature, such as morning glory and sea star. The reason why these plants and animals are formed to be pentagon may be the stability, like triangle.

As you know, US Headquarter of Department of Defense is called the pentagon, after the shape of building.

Below is the drawing method for pentagon, very interesting;

Draw a circle in which to inscribe the pentagon and mark the center point O. (This is the green circle in the diagram to the right).
Choose a point A on the circle that will serve as one vertex of the pentagon. Draw a line through O and A.
Construct a line perpendicular to the line OA passing through O. Mark its intersection with one side of the circle as the point B.
Construct the point C as the midpoint of O and B.
Draw a circle centered at C through the point A. Mark its intersection with the line OB (inside the original circle) as the point D.
Draw a circle centered at A through the point D. Mark its intersections with the original (green) circle as the points E and F.
Draw a circle centered at E through the point A. Mark its other intersection with the original circle as the point G.
Draw a circle centered at F through the point A. Mark its other intersection with the original circle as the point H.