Chain rule. Let g:Rn ->
Rp, f:Rp ->
Rm, and let h be the composition of f with g. That
is, h is f "circle" g or h(x)=f(g(x)). The chain rule
rule is given below. Remember, order matters in matrix multiplication!
Be able to use the chain rule.
Dh(x)=Df(g(x)) Dg(x) or
h'(x)=f'(g(x)) g'(x)