Consider the given expression.
2tanθ(1−tan2θ)secθ(1+tanθ)2
⇒2sinθcosθ(1−tan2θ)1cosθ(1+tanθ)2[∵sec2θ=1+tan2θ]
⇒2sinθ(1−tanθ)(1+tanθ)(1+tanθ)2
⇒2sinθ(1−tanθ)(1+tanθ)
Hence, this is the answer.