tan−1(3a2x−x3a3−3ax2),a>0;−a√3≤x≤a√3
Let x=a tanθ
⇒ xa=tanθ⇒θtan−1(xa)∴ tan−1(3a2x−x3a3−3ax2)=tan−1(3a2(a tan θ)−(a tan θ)3a3−3a(a tan θ)2)=tan−1(a3(3tan θ)−tan3θa3(1−3tan2θ))=tan−1(3 tan θ−tan3θ1−3tan2θ)=tan−1(tan 3θ)(∵ tan 3θ=3tan θ−tan3θ1−3tan2θ)=3θ=3tan−1(xa)