The solution of frac{1}{2} +cosx + cos2 | vedclass

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Question

$\frac{1}{2}+\frac{1}{2 \sin \frac{x}{2}} 2 \sin \frac{x}{2}(\cos x+\cos 2 x+\cos 3 x+\cos 4 x)=0$

$=\frac{1}{2}+\frac{1}{2 \sin \frac{x}{2}}\left(

Vedclass · Accepted Answer

$x=\frac{2n\pi}{9},n\in I,n
eq 9m,m\in I$

Vedclass · Answer

$\frac{1}{2}+\frac{1}{2 \sin \frac{x}{2}} 2 \sin \frac{x}{2}(\cos x+\cos 2 x+\cos 3 x+\cos 4 x)=0$

$=\frac{1}{2}+\frac{1}{2 \sin \frac{x}{2}}\left(\sin \frac{9 x}{2}-\sin \frac{x}{2}ight)=0$

$=\frac{\sin \left(\frac{9 \mathrm{x}}{2}ight)}{\sin \left(\frac{\mathrm{x}}{2}ight)}=0 $

$ \Rightarrow \mathrm{x}=\frac{2 \mathrm{n} \pi}{9}, \mathrm{n} 
eq 9 \mathrm{mm} \in \mathrm{I}$

The solution of $\frac{1}{2} +cosx + cos2x + cos3x + cos4x = 0$ is

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