Let α ∈ ( 0 , π 2 )   , be constant.If the integral ∫ t a n x + t a n α t a…

Let α(0,π2) , be constant.If the integral tanx+tanαtanx-tanαdx=Axcos2α+Bxsin2α+C, where C is a constant of integration, then the functions A(x) and B(x) are respectively
 
  1. x-α and logesinx-α
  2. x+α and logecosx-α 
  3. x+α and logesinx+α
  4. x-α and logecosx-α

Solution

I=tanx+tanαtanx-tanαdx=sinxcosx+sinαcosαsinxcosx-sinαcosαdx
=sinxcosα+cosxsinαsinxcosα-cosxsinαdx=sinx+αsinx-αdx
=sinx-α+2αsin(x-α)dx=sinx-αcos2α+cosx-αsin2αsin(x-α)dx
=cos2α+sin2αcotx-αdx
=xcos2α+sin2αlogesinx-α+C
=(x-α)cos2α+sin2αlogesinx-α+C
Hence, Ax=x-α and Bx=logesinx-α

Asked in: JEE Main 2019 (12 Apr Shift 2)

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