INVERSION, a term used in the study of geometric figures. To take a simple case, suppose in this figure that OP=I, and 0P2=2. Then OP1.OP2=0P. Let us say that Then it is evident that there is an infinite num ber of points Pi, P2 on the line such that A geometric transformation which replaces each point by a point such that is called an inversion. In such case 0 is the centre of inversion and k is the radius of inversion. As P1 moves
nearer to 0, moves farther away. As approaches P, also approaches P. In general we say that, when xy=k, x and y are inversely proportional, one decreasing as the other increases. We may also say that if y=f(x), we may inversely consider x as a function (implicit) of y.