1.

4 cos A cos(60-A) cos (60+A) = cos 3A

Answer»

4 COSA×cos60-A×cos60+A=Cos3A
4CosA×COS Sq 60 A=Cos3A
4CosA×1/2^2=cos3A[Cos 60=1/2]
CosA 1=Cos3A
0=Cos3A-Cos1A【zero PRODUCT rule】
0=Cos2A. Ans



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