Ok, let me clarify. I attempted to take the derivative of each separate part (thus, e^-t became -e^(-t) and so on), but I don't know what to do with it.
Question:
If f is a vector-valued function defined by f(t)=(e^(-t), cos(t)), find f''(t).
I'm not even quite sure how to start.
Any help would be loved! Thank you!