Posted by **jake** on Monday, November 10, 2008 at 2:01am.

Find the roots of z^6 + 1 and hence resolve z^6 + 1into read quadratic factors; deduce that

cos3x = 4[cos(x) -cos(pi/6)][(cos(x) -cos(pi/2)][(cos(x) -cos(5pi/6)]

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