The correct option is B −2x√(1+x2)sin(lnx)
Let y=ln(√1+x2+x√1+x2−x)
⇒y=ln(√1+x2+x)−ln(√1+x2−x)⇒dydx=(1+2x2√1+x2)√1+x2+x−(2x2√1+x2−1)√1+x2−x⇒dydx=1√1+x2+1√1+x2⇒dydx=2√1+x2
Let z=cos(lnx)
⇒dzdx=−sin(lnx)x
Therefore, dydz=dydx×dxdz
⇒dydz=−2x√1+x2sin(lnx)