What is the surface area of a triangle 13 ft x 13 ft x 18 ft
There is this wonderful expression called Heron's formula that says
If the sides of the triangle are a, b, c, and the semiperimeter is s (s = (a+b+c)/2), then the area is .
When the sides are of length 13, 13 and 18 feet, s = 22 feet and thus the area is
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