Please solve 3./ cos3x - sin 3x + 2cosx = 0
Last edited by mr fantastic; Jul 21st 2009 at 05:56 PM. Reason: Moved question to new thread and edited accordingly
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Originally Posted by mp3qz Please solve 3./ cos3x - sin 3x + 2cosx = 0 Maybe you could consider $\displaystyle \sin(3x) = 3 \sin(x)-4\sin^3(x)$ and $\displaystyle \cos(3x) = 4\cos^3(x)- 3 \cos(x)$
Originally Posted by pickslides Maybe you could consider $\displaystyle \sin(3x) = 3 \sin(x)-4\sin^3(x)$ and $\displaystyle \cos(3x) = 4\cos^3(x)- 3 \cos(x)$ Using the hint of pickslides the equation becomes $\displaystyle 4\sin^3x+4\cos^3x-3\sin x-\cos x=0$ which is the same equation like in this thread: http://www.mathhelpforum.com/math-he...-equation.html
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