OK geniuses...I have an equilateral triangle that is 20" from point to point to point. If I draw a circle that hits all three points, what's the diameter of the circle?

If I spent some time online looking for the formulas, I might be able to figure this out, but I know you guys are geniuses, so, solve for X, please.

Oh...I have an upright compressor with 3 feet. I want to put it on a square pad and need to know what dimensions to make the square.