Re: Problem from Google Answers

From: mjtg@xxxxxxxxxxxxx (M.J.T. Guy)
Date: 13 May 2005 17:21:38 GMT

Justin Young <x_static66@xxxxxxxxxxx> wrote:
>Prove that there are infinitely many x in the interval [0,pi/2] such that
>both sin x and cos x are rational.

Take any (a, b, c) satisfying a^2 + b^2 = c^2.
Then arcsin(a/c) = arccos(b/c) is a suitable value for x.

Mike Guy
.

References:
- Problem from Google Answers
  - From: Justin Young

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