A pentagon has five sides and five interior angles which add up to a total of 540 degrees. To determine the number of degrees of the interior angles in a pentagon requires subtracting two from the number of sides (five) and multiplying by 180.
The prefix penta- in pentagon is from the Greek and means "five," according to Dictionary.com. Regular pentagons have all equal sides and all equal angles, while the degrees of angles and lengths of sides vary in an irregular pentagon. The angles are each 108 degrees in a regular pentagon. The Pentagon in Washington, D.C. is a large five-sided construction that houses the Department of Defense for the United States government.