If cos theta + cos 2theta + cos 3theta = 0, t | vedclass

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Question

$\cos 	heta + \cos 2	heta + \cos 3	heta = 0$ 

==> $(\cos 	heta + \cos 3	heta ) + \cos 2	heta = 0$

==> $2\cos 2	heta \cos 	het

Vedclass · Accepted Answer

$(a)$ and $(b)$ both

Vedclass · Answer

$\cos 	heta + \cos 2	heta + \cos 3	heta = 0$ 

==> $(\cos 	heta + \cos 3	heta ) + \cos 2	heta = 0$

==> $2\cos 2	heta \cos 	heta + \cos 2	heta = 0$

==> $\cos 2	heta (2\cos 	heta + 1) = 0$ 

==> $\cos 2	heta = 0 = \cos \frac{\pi }{2}$

==> $	heta = \frac{\pi }{4}$

==> $	heta = 2m\pi \pm \frac{\pi }{4}$

or $\cos 	heta = \frac{{ - 1}}{2} = \cos \frac{{2\pi }}{3}$ 

==> $	heta = 2m\pi \pm \frac{{2\pi }}{3}$.

If $\cos \theta + \cos 2\theta + \cos 3\theta = 0$, then the general value of $\theta $ is

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