For now, the problem we want to solve is this:
Given the conditions described in the text above and in the diagrams, and given an angle for the squatter's ankle joint (call this angle ), we want to determine the X-Y position of the squatter's knee joint. Remember: the weight must always be directly over the feet.
The angle will be measured in degrees counterclockwise from the positive X axis. (Or more precisely, will be measured in degrees counterclockwise, from a ray in the positive X direction passing though the ankle joint, to the shin link.) So when the squatter is standing straight up, the ankle joint angle will be 90 degrees.