If ∫ d θ cos 2 θ tan 2 θ + sec 2 θ = λ tan θ + 2 log e f θ + C…

If dθcos2θtan2θ+sec2θ= λtanθ+2logefθ+C where C is a constant of integration, then the ordered pair λ,fθ is equal to:
  1. 1,1-tanθ
  2. -1,1-tanθ
  3. -1,1+tanθ
  4. 1,1+tanθ

Solution

sec2θ1+tan2θ1-tan2θ+2tanθ1-tan2θdθ

=sec2θ1-tan2θ1+tanθ2dθ

=sec2θ1-tanθ1+tanθdθ

Let tanθ=tsec2θdθ=dt

=1-t1+tdt=-1+21+tdt

=-t+2ln1+t+C

=-tanθ+2ln1+tanθ+C

λ=-1 and fθ=1+tanθ

Asked in: JEE Main 2020 (09 Jan Shift 2)

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