The figure shown above is a regular pyramid with equilateral triangle as a base. Find the volume in cubic units rounded to the nearest whole number.
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Solve for x by cosine law,
6 2 = x 2 + x 2 − 2 ( x ) ( x ) c o s 1 2 0
x = 2 3
Solve for h by Pythagorean Theorem
h = 8 2 − x 2 = 6 4 − 1 2 = 5 2
Solve for the area of the base,
A b = 2 1 ( 6 2 ) ( s i n 6 0 ) = 1 8 s i n 6 0
Now solve for the volume,
V = 3 1 A b h = 3 1 ( 1 8 s i n 6 0 ) ( 5 2 ) = 3 7 c u b i c u n i t s