Help me pleaseeee?

Question

I'm supposed to derive this: y = e^(-8x) cos(3x)

I got -3sin(exp(x))exp(-8x) -8cos(3x)exp(-8x)

but its not right..any help would be appreciated.

Answer 1

y = e^(-8x) cos(3x)
y' = e^{-8x} (-sin(3x) 3) + (-8) e^{-8x} cos(3x)

Answer 2

The verb for taking a derivative is not "to derive". It is "to differentiate".

When you differentiate e^(-8*x)*cos(3*x) with respect to x, you get:

-e^(-8*x) * (8*cos(3*x) + 3*sin(3*x))