1)prove that (cos x)cos(60-x)cos(60+x) = ¼ cos3x 2)sin 2x -sin5x + sin6x = 0

1)prove that (cos x)cos(60-x)cos(60+x) = ¼ cos3x 
2)sin 2x -sin5x + sin6x = 0


1 Answers

Sourabh Singh IIT Patna
askIITians Faculty 2104 Points
6 years ago
Use exopansion property of cos(A+B) and apply
you will get the answer.
Take sin5x on other side and then use the clubbing property of sinA+sinB.

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