Imagine a plain (x,y) with 3 points (x1,y1), (x2,y2), (x3,y3) at it, not positioned in a line.
At each of the 3 points is fixed a straight wire with given length L1, L2, L3, protruding to z-space.
Find the spatial coordinates of the point (x,y,z), where the 3 ends of the wires can find together.
From Wolfgang Issel using MC14 on Windows 7