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Question: Find the area of an equilateral triangle with height 8in.


A ) (643) in2
B ) (163) in2
C ) (653) in2
D ) (323) in2

Steps to derive

1 Let a be length of the side of the equilateral triangle whose height is 8 in. as shown.


2 sin 60° = ha=8a
 [Use the sine ratio.]

3 32=8a

4 a = 163
 [Cross - product property.]

5 So, area of the equilateral triangle = (12) side length × side length × sin 60°.
 [Write the area of an equilateral triangle.]

6 = (12)(163)(163) sin 60° = (643) in2.
 [Substitute the value of a.]



Hence the right answer is Option A

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