Answer
(a) $$g(x)=3 \sin x \qquad h(x)=x^2$$
(b) $$g(x)=3x^2+4x \qquad h(x)= \sin x$$
Work Step by Step
(a) By considering the functions $$g(x)=3 \sin x \qquad h(x)=x^2$$ we have $$f(x)=(g \circ h)(x)=g(h(x))=3 \sin (x^2).$$
(b) By considering the functions $$g(x)=3x^2+4x \qquad h(x)= \sin x$$ we have $$f(x)=(g \circ h)(x)=g(h(x))=3 \sin ^2 x + 4 \sin x.$$
