Well assuming that you start with a 60/60/60 triangle, if you drop a line from the apex down you have two right angle triangles. The basic formula for them is a(sq) + b(sp) = c(sq) where a and b are the two sides that form the rightangle and c is the long hypoteneuse/diagonal side.
So if you know the length of one side of your triangle you can work out the height.
If your triangles have 3" long sides they will have a height of - (1/2 X 3)sp + (height?) = 3(sq) height = (3 X 3) - (1.5 X 1.5) = just a shade over 2" (about 2.04")
There are other ways to work this out (using logarithms, etc) but I am limited mathematically to just the basic formulas, and I find a(sq) + b(sp) = c(sq) is almost all I need for quilting. You might have to do your figuring in a couple of steps, but this can be used to measure most patchwork shapes.
Does that help any?