Let S be a lamina in the xy-plane with center of mass at the origin, and let L be the line ax + by = 0, which goes through the origin. Show that the (signed) distance d of a point (x, y) from L is d = (ax + by)/((2 + b2, and use this to conclude that the moment of S with respect to L is 0. This shows that a lamina will balance on any line through its center of mass.