Hi, I visited my Mother and Stepfather recently, and admired the tall trees around their house. We estimated them to be around 180-200 feet tall. I told my Stepfather that the *Actual* height could of course be calculated. I said there are three angles and three lengths for any triangle, and if you have any three of them, you can calculate the others. (I said a bit less than that, but that was my idea). He said the Pythagorean theorem is the only way to calculate the height of the tree, and it is not practical because we can't measure the distance from the apex to the observer. I said I just need to stand at a fixed distance D, from the tree, and measure the angle A made by a straight line from that point to the apex, relative to a straight line from that point to the base of the tree. The tree grows straight, so its angle to the ground is 90*. He told me I was a fool. And I told him I'd prove him wrong later. From a logical standpoint, if two angles are fixed and one length is known, the other two lengths MUST intersect at only one point. If they can only have one intersection, they can only have one length. I really doubt it's impossible to calculate it, but it might take a little more than A^2 + B^2 = C^2.