Question 225950
if the perimeter is P, then one side is P/3


because half of the equilateral is a 30-60-90 right triangle; that makes the base P/3 and the height (P√3)/6


A = 1/2 * b * h = 1/2 * P/3 * (P√3)/6 = (P^2 * √3) / 36