In geometry, a pentagon is a polygon with 5 sides. Each angle of a regular pentagon is . The sum of the internal angles of any pentagon is .
It is possible to construct a regular pentagon with compass and straightedge:
1. Draw circle (red).
2. Draw diameter and construct a perpendicular radius through .
3. Construct the midpoint of , and label it .
4. Draw (green).
5. Construct the angle bisector of , and label its intersection with as (pink).
6. Construct a perpendicular to at .
7. Adjust your compass to length , and mark off points , and on circle .
8. is a regular pentagon.
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