What is the area of the regular pentagon of side 6 cm?
(Corr to 3 sig.fig)
Mathematics F.2
2008-06-17 6:32 am
回答 (2)
2008-06-17 6:46 am
✔ 最佳答案
Area of polygon = nL^2/[4tan(180/n)]. Now n= 5, L = 6. Therefore, area= 5(6)(6)/[4tan(180/5)] = 45/tan36 = 61.9cm2 (3 sig.fig.)
2008-06-17 6:49 am
The regular pentagon consists of 5 triangles with 72 (360/5) angle at the center point of the pentagon.
the height of triangle = 3 / tan 36 = 4.129
The area of each triangle = 0.5 ( 6)(4.129) = 12.387 sq. cm.
the area of pentagon = 5 (area of triangle) = 5 (12.387)
= 61.9 sq. cm.
the height of triangle = 3 / tan 36 = 4.129
The area of each triangle = 0.5 ( 6)(4.129) = 12.387 sq. cm.
the area of pentagon = 5 (area of triangle) = 5 (12.387)
= 61.9 sq. cm.
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