Solve for x:tan−1(x−1)+tan−1x+tan−1(x+1)=tan−13x.
OR
Prove that : (6x−8x31−12x2)−tan−1(4x1−4x2)=tan−12x;|2x|<1√3.
Given that tan−1(x−1)+tan−1x+tan−1(x+1)=tan−13x
⇒tan−1(x−1)+tan−1(x+1)=tan−13x−tan−1x ⇒tan−1(x−1)+(x+1)1−(x−1)(x+1)=tan−13x−x1+3x.x⇒tan−12x2−x2=tan−12x1+3x2 ⇒2x2−x2=2x1+3x2⇒2x(1+3x2−2+x2)=0Either 2x=0 or (4x2−1)=0 ∴x=0 or x=±12.OR LHS=Let y=tan−1(6x−8x31−12x2)−tan−1(4x1−4x2) Put 2x=tan θ⇒θ=tan−12x...(i)∴y=tan−1(3 tan θ−tan3 θ1−3 tan2 θ)−tan−1(2 tan θ1−tan2 θ)⇒y=tan−1(tan 3θ)−tan−1(tan 2θ)⇒y=3θ−2θ=θ=tan−12x=RHS. By(i)