Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.



Re: How to prove that cos(10°) is not rational ?
Posted:
Sep 22, 2007 4:36 PM


egouello@gmail.com wrote: > Hello, > I already know that cos(x) is irrational when 0°<x<90° and x<>60° but > I don't find the proof on the Web. > Does someone have a reference for that?
Here's a previous sci.math thread on this subject:
http://groups.google.com/group/sci.math/browse_frm/thread/ebac71b907f1f18c
 Ben



