File:Inversion by Stereographic.png

Summary

${\displaystyle \triangle NOP^{\prime }\sim \triangle P^{\prime \prime }OS\implies OP^{\prime }:ON=OS:OP^{\prime \prime }\implies OP^{\prime }\cdot OP^{\prime \prime }=r^{2}}$

Licensing

I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.