(a) Find $f'(x)$ if $f(x)=x^{3 x}$. [Hint: $x^{3 x}=e^{\ln(x^{3 x})}=e^{3 x\ln{x}}$]
(b) Find $g'(x)$ if $g(x)=x^{\sin(3 x)}$.

(a) $f'(x) =$
(b) $g'(x) =$