The derivative of cos(x) is -sin(x).
So f '(x) = (x^3)' * cos(x) + x^3*(cos(x))' ...
= (3x^2)cos(x) - sin(x)x^3
h(x) = sq.root(t) * (1-t^2)
and
f(x)=x^3 cos x
I know the answers, but I don't know how to differentiate with a square root involved or trig function involved. I need the work to show me what I'm suppose to do. Thanks!