verify the identify: since cos2u=cos^2-sin^2 would the same be applied to cos3u..as in = cos^3-sin^3, or am i wrong
Last edited by algebra2; Apr 17th 2008 at 07:12 PM. Reason: anaLytical reasons
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Originally Posted by algebra2 verify the identify: since cos2u=cos^2-sin^2 would the same be applied to cos3u..as in = cos^3-sin^3, or am i wrong $\displaystyle cos(A + B) = cos(A)~cos(B) - sin(A)~sin(B)$ Soooo.... $\displaystyle cos(3 \theta) = cos(2\theta + \theta)$ $\displaystyle = cos(2\theta)~cos(\theta) - sin(2\theta)~sin(\theta)$ and you can take it from here. -Dan
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