cos 20^circ cos 40^circ cos 80^circ = | vedclass

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(D) We use the formula $\cos 	heta \cos(2	heta) \cos(4	heta) = \frac{\sin(8	heta)}{8\sin 	heta}$.Here,$	heta = 20^\circ$.So,$\cos 20^\circ \cos

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$1/8$

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(D) We use the formula $\cos 	heta \cos(2	heta) \cos(4	heta) = \frac{\sin(8	heta)}{8\sin 	heta}$.Here,$	heta = 20^\circ$.So,$\cos 20^\circ \cos 40^\circ \cos 80^\circ = \frac{\sin(8 	imes 20^\circ)}{8 \sin 20^\circ}$.$= \frac{\sin 160^\circ}{8 \sin 20^\circ}$.Since $\sin 160^\circ = \sin(180^\circ - 20^\circ) = \sin 20^\circ$,$= \frac{\sin 20^\circ}{8 \sin 20^\circ} = \frac{1}{8}$.

$\cos 20^\circ \cos 40^\circ \cos 80^\circ = $

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