Given that:
\(y = \log[\log (\sin x)]\)
\(\therefore \frac{dy}{dx} = \frac d{dx} \log[\log(\sin x)]\)
\(= \frac 1{\log(\sin x)} . \frac d{dx} (\sin x)\)
\(= \frac 1{\log(\sin x)} . \frac 1{\sin x} . \frac d{dx} \sin x\)
\(= \frac 1{\log(\sin x)} . \frac 1{\sin x} . \frac {\cos x}1\)
\(= \frac {\cot x}{\log (\sin x)}\)