cos A + cos (240^circ + A) + cos (240^circ - | vedclass

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Question

(b) $\cos A + \cos \,({240^o} + A) + \cos \,({240^o} - A)$

$ = \cos A + 2\cos {240^o}\cos A$

$ = \cos A\{ 1 + 2\cos ({180^o} + {60^o})\} $

$=

Vedclass · Accepted Answer

$0$

Vedclass · Answer

(b) $\cos A + \cos \,({240^o} + A) + \cos \,({240^o} - A)$

$ = \cos A + 2\cos {240^o}\cos A$

$ = \cos A\{ 1 + 2\cos ({180^o} + {60^o})\} $

$= \cos A\,\left\{ {1 + 2\,\left( { - \frac{1}{2}} \right)} \right\}$

$ = 0$.

$\cos A + \cos (240^\circ + A) + \cos (240^\circ - A) = $

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