Small trig questions, please help me... Watch

Samsoonie
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#1
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The question is;

(a) Find the expression of cos5x in terms of sinx and cosx.
(b) Find the expression of sin6x in terms of sinx.

Thanks in advance for any help.
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angelafleming
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Use De Moivre's theorem:
(cos\theta+isin\theta)^n=cos\ n\theta+i sin\ n\theta
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Samsoonie
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(Original post by angelafleming)
Use De Moivre's theorem:
(cos\theta+isin\theta)^n=cos\ n\theta+i sin\ n\theta
Thanks for your help but I think this theorem is quite advanced for me (Just few months since I started IB Maths Higher Level (roughly equals to A-levels Maths + Further Maths).
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ForGreatJustice
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well you could just use double angle formulae... but you'd be a braver soul than I
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