This example demonstrates how to construct a pentagon using a straight edge and ruler.

Start by drawing a circle whose size is proportional to the size of the pentagon you want to draw. Place a point at the center of the cicle draw a vertical line for the diameter of the circle.

Draw a perpendicular line leftwards from the center of the circle. Draw a point where the line intersects with the circle.

Bisect this line segment formed between the new point and the center of the circle.

Draw a circle at this new point with a diameter equal to the radius of the starting circle. Then draw a line from the bottom-most point through of the center of the circle. Draw points at the two places the line intersects with the circle.

Draw another circle and draw the points of intersection.

Draw another circle and draw the points of intersection.

Connect the five points along the perimeter to form the pentagon.

We have finished constructing the pentagon.

How to construct a perpendicular line given a straight line.

This exampls shows how to bisect a line with compass and straight edge.