Let f be a one-to-one correspondence of the points in a plane. Prove or disprove the following statement:

"If f maps circles to circles, then it maps straight lines to straight lines."

If I could prove that the inverse of f mapped circles to circles, then I could easily prove that f maps lines to lines. Alas, I cannot.

Posted by Bractals on 2006-11-15 18:48:19