As shown in the diagram, one end of a -foot-long electric cable is fixed at point on the wall, and the other end of the cable (denoted by ) is a sensor. There is a pin attached to the cable at a point that is units away from , and the pin can be fixed to any point on the wall reachable by . Due to gravity, the free part of the cable (i.e. ) is always perpendicular to the ground A few other measurements are provided in the diagram. What is the minimum distance between and
