Please help me..

Thanks,

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- Jul 19th 2013, 07:01 AMkjchauhanexpansion of cos
Please help me..

Thanks, - Jul 19th 2013, 07:09 AMProve ItRe: expansion of cos
Why not just apply the MacLaurin Series formula to the function cos(x)?

- Jul 19th 2013, 10:13 AMtopsquarkRe: expansion of cos
Probably can't because this is in Pre-University Trigonometry.

@kjchauhan

My only problems with this as a "proof" is your original statement: $\displaystyle cos(n \theta) = \text{...}$. Was this given?

My other problem is your limit statement: $\displaystyle \lim_{\theta \to 0} \frac{sin ( \theta )}{ \theta } = 1$. Was this given as well?

If they are given, it looks great. If they are not given then you have some more work to do.

-Dan