dch on The Fifth problem: math and anti-Semitism in the Soviet Union · Hackerly

Comment on The Fifth problem: math and anti-Semitism in the Soviet Union parent

The concept he's talking about is http://en.wikipedia.org/wiki/Circle_inversion; http://mathworld.wolfram.com/Inversion.html has a bit more detail.

Thanks, and the problem in question is actually http://en.wikipedia.org/wiki/Problem_of_Apollonius