If θ=tan−1(2tan2θ)−tan−1(13tanθ), then tanθ=
-2
-1
23
2
We have θ=tan−12tan2θ−13tanθ1+23tan3θ
⇒tanθ=6tan2θ−tanθ3+2tan3θ⇒1=6tanθ−13+2tan3θ or tanθ=0⇒2tan3θ−6tanθ+4=0⇒(tanθ−1)2(tanθ+2)=0⇒tanθ=1;tanθ=−2;tanθ=0