यदि x + y + z = {180^o}, तो cos 2x + cos 2y - | vedclass

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Question

(b) $\cos 2x + \cos 2y - \cos 2z$ 

$ = 2\cos (x + y)\cos (x - y) - 2{\cos ^2}z + 1$ 

$ = 2\cos (\pi - z)\cos (x - y) - 2{\cos ^2}z + 1

Vedclass · Accepted Answer

$1 - 4\sin x.\,\sin y.\,\cos z$

Vedclass · Answer

(b) $\cos 2x + \cos 2y - \cos 2z$ 

$ = 2\cos (x + y)\cos (x - y) - 2{\cos ^2}z + 1$ 

$ = 2\cos (\pi - z)\cos (x - y) - 2{\cos ^2}z + 1$ 

$ = 1 - 2\cos z\{ \cos (x - y) - \cos (x + y)\} $

$ = 1 - 2\cos z2\sin x\sin y = 1 - 4\sin x\sin y\cos z$.

यदि $x + y + z = {180^o},$ तो $\cos 2x + \cos 2y - \cos 2z$ बराबर है

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