1.

`int_0^(pi//6)cosxcos2x dx`A. `(1)/(4)`B. `(5)/(12)`C. `(1)/(3)`D. `(7)/(12)`

Answer» `I=(1)/(2)int_(0)^(pi//6)[cos3x+cosx]dx=(1)/(2)[(sin3x)/(3)+sinx]_(0)^(pi//6)=(15)/(12)`.


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