Q.

Let 2-tanx3+tanxdx=12(αx+loge|βsinx+γcosx|)+C, where C is the constant of integration. Then α+γβ is equal to:              [2024]

1 7  
2 3  
3 1  
4 4  

Ans.

(4)

Let I=2-tanx3+tanxdx=2cosx-sinx3cosx+sinxdx

Write Numerator=λ(Differentiation of Denominator)+μ(Denominator)

2cosx-sinx=λ(-3sinx+cosx)+μ(3cosx+sinx)

λ+3μ=2                 (i)

and -3λ+μ=-1                   (ii)

From equations (i) and (ii), λ=μ=12

I=12-3sinx+cosx3cosx+sinxdx+123cosx+sinx3cosx+sinxdx

=12dtt+12dx  [Putting 3cosx+sinx=t in first integral (-3sinx+cosx)dx=dt]

=12ln(t)+12x+C

=12ln|3cosx+sinx|+12x+C

=12(αx+loge|βsinx+γcosx|)+C  (∵Given)

α=1,β=1,γ=3

Now, α+γβ=1+31=4