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October 21, 2014

Homework Help: Math - complex numbers

Posted by Chiquesta on Saturday, December 17, 2011 at 12:59am.

These questions are related to de moivre's theorem:

z^n + 1/z^n = 2cosntheta
z^n - 1/z^n = 2 isin ntheta


1. Express sin^5theta in the form Asintheta + Bsin3theta + Csin5theta and hence find the integral of sin^5theta.


2. Express sin^6theta in multiples of costheta and hence evaluate the integral of sin^6theta between 0 and pi/2.


3. Evaluate the integral of cos^7theta between pi/2 and 0.


The answers are:
1. -1/80cos5theta + 5/48cos3theta - 5/8costheta

2. 5pi/32

3. 5pi/32

Could you please guide me through the solutions, thank you SO much :)

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