# Difference between revisions of "Pentagon"

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In [[geometry]], a '''pentagon''' is a [[polygon]] with 5 sides. Each [[angle]] of a [[regular polygon | regular]] pentagon is <math>108^{\circ}</math>. The sum of the internal angles of any pentagon is <math>540^{\circ}</math>. | In [[geometry]], a '''pentagon''' is a [[polygon]] with 5 sides. Each [[angle]] of a [[regular polygon | regular]] pentagon is <math>108^{\circ}</math>. The sum of the internal angles of any pentagon is <math>540^{\circ}</math>. | ||

− | + | == Construction == | |

It is possible to construct a regular pentagon with compass and straightedge: | It is possible to construct a regular pentagon with compass and straightedge: |

## Revision as of 23:08, 5 May 2007

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 .

## Construction

It is possible to construct a regular pentagon with compass and straightedge:

http://img164.imageshack.us/img164/1296/pentagonconstructiongt4.png

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.

## See also

*This article is a stub. Help us out by expanding it.*