How do you differentiate f(x)=cos(e^(3x^2)+7) using the chain rule?

1 Answer
Jul 10, 2016

f^'=-6xe^(3x^2)sin(e^(3x^2)+7)

Explanation:

I prefer to use the form (dy)/(dx)

Let u=e^(3x^2)+7=>" "(du)/(dx)=6xe^(3x^2)

Write f(x)" as " y=cos(u)=>" "(dy)/(du)=-sin(u)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
But (dy)/(dx)=(dy)/(cancel(du))xx(cancel(du))/(dx)

=> (dy)/(dx)=(6xe^(3x^2))(-sin(e^(3x^2)+7))

=> (dy)/(dx)=-6xe^(3x^2)sin(e^(3x^2)+7)

Or if you prefer f^'=-6xe^(3x^2)sin(e^(3x^2)+7)

As confirmation:
Tony B - Maple