The reciprocal of a real or complex number is its multiplicative inverse . The reciprocal of a complex number is given by

Given a geometric figure consisting of an assemblage of points, the polars with respect to an inversion circle constitute another figure. These figures are said to be reciprocal with respect to each other. Then there exists a duality principle which states that theorems for the original figure can be immediately applied to the reciprocal figure after suitable modification (Lachlan 1893).

 

Inversion, Inversion Pole, Polar, Reciprocal Curve, Reciprocation