integrate sin4x*cos7x dx

Dear student,

Write cos7x as cos(4x+3x) and then use cos(A+B) formula

also use sinxcosx=sin2x/2

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Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

I = sin4xcos7x dx

(2sinacosb = sina+b + sina-b)

I = 2sin4xcos7xdx/2

by using formula

I = [sin(4x+7x) + sin(4x-7x) ]dx/2

I = [sin11x + sin(-3x)]dx/2

I = [sin11x - sin3x ]dx/2                       (sin(-x) = -sinx)

I = -cos11x/22 + cos3x/6 + C