Q24 of 123 Page 9

Mark the Correct alternative in the following:

2(1 – 2 sin2 7x) sin 3x is equal to


Given expression is 2(1 – 2 sin2 7x) sin 3x


2(1 – 2 sin2 7x) sin 3x = 2 cos 2(7x) sin 3x


[ using cos 2A = 1 – 2sin2A ]


= 2 cos 14x sin 3x


[using the sum of angles formula ]



= sin (17x) – sin (11x)


Therefore 2(1 – 2 sin2 7x) sin 3x = sin (17x) – sin (11x)


The answer is option A.

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