Posted by cindy on Thursday, January 12, 2012 at 5:59pm.
Find the area of a regular pentagon with a side of 6 ft. Give the answer to the nearest tenth.
ok can't remember how to do this

geometry  Reiny, Thursday, January 12, 2012 at 6:31pm
A regular pentagon can be drawn as 5 conguent isosceles triangles with a central angle of 72° each, and equal base angles of 54°.
So just find the area of one of these by first finding the altitude of one of them
tan 54° = h/3
h = 3tan54°
area of one of them = (1/2)base x height
= (1/2)(6)(3tan54)
= 9tan 54°
so the whole pentagon = 45tan 54°
= appr. 61.9 square ft

geometry  Shay, Thursday, January 12, 2012 at 6:33pm
You forgot to give us the lenght of the side of the line that connects from the middle of the pentagon to a side of the pentagon.

geometry  Steve, Friday, January 13, 2012 at 12:00am
It's there; you just need to recognize it:
h = 3tan54°
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