It's easy to see that is n is an odd positive integer,
and if n is an even positive integer,
But how would you prove that?
Last edited by Random Variable; February 23rd 2010 at 10:12 PM.
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By induction ?
Or else, use what you know about odd numbers : if n is even, n=(n-1)+1, where (n-1) is odd.
and use the addition formula for the sine function.
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