I need to find the perimeter and area of a regular polygon, (an equilateral triangle) but I only have one side length of this triangle and it's 18. I know the perimeter is 18x3, but how do I find the area? I can't use any sort of Trig. I've heard something like the 30,60,90 triangle or something...and that the apothem is square root 3/2, the side is 1/2s and the other side is s. Does this make sense? The answer is 81 times the square root of 3 squared units. I don't know how to get to the answer, though.