Greetings! Is the problem asking to take the derivative of sin(cos((x2-1)1/3)? If so, it looks like you're on the right track, although I'm not sure why (x2-1)-2/3 was factored out. Just keep applying the chain rule.
[tex]\frac{d}{dx}[\sin(\cos((x^2-1)^{1/3}))][/tex]
[tex]=\cos(\cos((x^2-1)^{1/3})) \frac{d}{dx}[\cos((x^2-1)^{1/3}))][/tex]
[tex]=\cos(\cos((x^2-1)^{1/3})) (-\sin((x^2-1)^{1/3}))\frac{d}{dx}[(x^2-1)^{1/3}][/tex]
[tex]=-\cos(\cos((x^2-1)^{1/3}))\sin((x^2-1)^{1/3})((1/3)(x^2-1)^{-2/3})\frac{d}{dx}[x^2-1][/tex]
[tex]=-\cos(\cos((x^2-1)^{1/3}))\sin((x^2-1)^{1/3})((1/3)(x^2-1)^{-2/3})(2x)[/tex]
[tex]=\frac{-2x\cos(\cos((x^2-1)^{1/3}))\sin((x^2-1)^{1/3})}{3(x^2-1)^{2/3}}[/tex]