# Cosine fixpoint

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• May 23rd 2009, 07:28 AM
espen180
Cosine fixpoint
Is the cosine fixpoint (the solution to the equation $x=\cos x$) rational or irrational, and is it possible to prove it?
• May 25th 2009, 01:01 AM
Grandad
Rational or irrational
Hello espen180
Quote:

Originally Posted by espen180
Is the cosine fixpoint (the solution to the equation $x=\cos x$) rational or irrational, and is it possible to prove it?

I can't imagine that it could possibly be rational, but I have no idea how you might set about proving it!

Grandad