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How do you do this properly

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Ahmad:

--- Quote from: coblin on December 09, 2007, 09:11:12 pm ---* Sum of interior angles of a pentagon:
* Area of a regular pentagon (in terms of side length, S):

--- End quote ---



There's 5 triangles, with angles summing to 180 * 5 = 900. Now, the center angles add up to 360. So the sum of the interior angles of a regular pentagon is 900 - 360 = 540.

Drawing a perpendicular to the sides that meets with the center, immediately shows that as required.

kingmar:
That's rape. Ahmad, I want your epsilons. :D

/0:
Hi, someone posted a similar question on Mathhelpforum, the solution is quite nice:

http://www.mathhelpforum.com/math-help/geometry/24255-triangle-height.html

Ahmad:
That's the same solution, using trigonometry. Coblin and I have simply elaborated (in simple steps) and added a few unnecessary extensions to get an answer without a calculator (exact form).  ;D

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