Hi I am asked to tackle this one below I dont want to multiply the cosx by the cos2x yet all other routes I hit a dead end. Any help would be great
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Originally Posted by 200001 Hi I am asked to tackle this one below I dont want to multiply the cosx by the cos2x yet all other routes I hit a dead end. Any help would be great $\displaystyle \cos x(\frac{\cos^2 x-\sin^2 x}{\cos x+\sin x})=\frac{1}{2}$ $\displaystyle \cos x (\frac{(\cos x+\sin x)(\cos x-\sin x)}{\cos x+\sin x})=\frac{1}{2}$ Some simplication , $\displaystyle 2\cos ^2 x-1-2\cos x\sin x=0$ $\displaystyle \cos 2x=\sin 2x $
brilliant, thanks I made the error of trying to keep cos2a in its 'nice form' in the numerator
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