If cos 7theta = cos theta - sin 4theta , then | vedclass

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Question

(c) $\sin 4	heta = \cos 	heta - \cos 7	heta $

==> $\sin 4	heta = 2\sin (4	heta )\sin (3	heta )$

$ \Rightarrow $ $\sin 4	heta = 0 $

Vedclass · Accepted Answer

$\frac{{n\pi }}{4},\frac{{n\pi }}{3} + {( - 1)^n}\frac{\pi }{{18}}$

Vedclass · Answer

(c) $\sin 4	heta = \cos 	heta - \cos 7	heta $

==> $\sin 4	heta = 2\sin (4	heta )\sin (3	heta )$

$ \Rightarrow $ $\sin 4	heta = 0 $

$\Rightarrow $ $4	heta = n\pi $

or $\sin 3	heta = \frac{1}{2} = \sin \left( {\frac{\pi }{6}} ight)$

$ \Rightarrow $ $3	heta = n\pi + {( - 1)^n}\frac{\pi }{6} $

$\Rightarrow 	heta = \frac{{n\pi }}{4},\,\frac{{n\pi }}{3} + {( - 1)^n}\frac{\pi }{{18}}$.

If $\cos 7\theta = \cos \theta - \sin 4\theta $, then the general value of $\theta $ is

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