I was just about to say all that...the vector thing.

lol It's one of the few things I remember with passion from my physics classes.
They had to figure all this out because of hip replacement surgery. The farther out you place your leg away from the hip, the higher the force acting on your hip socket. Your hip abductor muscles try to keep the joint in place but aren't all that strong in relation to your quads. It's no surprise that long time lifters have bad joints.