You devil
This one has me bafflled.
I solved the 2 triangles trigonometrically in the xy plane to get the hypotenuses, then used each hypotenuse separately to get the altitude of the object in the z plane by the tangent of the elevation angle. I know I got the triangles properly solved because I verified the dimensions with the Pythagorean Theorem.
But I got two separate values for the altitude from each triangle when they should have been identical--508.47 ft vs 520.88 ft. I know it wasn't round-off error because I used my HP48 which has about a zillion significant digits.
I'm stumped, I probably made some fundamental geometry error but I'll be damned if I can find it.