જો $A + B + C = \pi ,$ તો $\cos \,\,2A + \cos \,\,2B + \cos \,\,2C = $
જો $A + B + C = \pi ,$ તો $\cos \,\,2A + \cos \,\,2B + \cos \,\,2C = $
- A
$1 + 4\,\cos A\,\cos B\,\sin C$
- B
$ - 1 + 4\,\sin A\,\sin B\,\cos C$
- C
$ - 1 - 4\,\cos A\,\,\cos B\,\,\cos C$
- D
એકપણ નહિ.
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