Question

how to integrate cos(3x) * e^(-4t) dt

Answer 1

i need help plz

Answer 2

Based on what you have there, the cos(3x) is going to be a constant when integrated with respect to t.

Answer 3

no sorry its cos (3t) not 3x

Answer 4

Well, there are a couple of ways. One which might be more practical, or not. Anyway, I'm lazy so I would use integration by parts and leave my answer in form of a function plus an integral.

Answer 5

Try to use this formula:

integral exp(alpha t) cos(beta t) dt = (exp(alpha t) (alpha cos(beta t)+beta sin(beta t)))/(alpha^2+beta^2)

in your problem alpha=-4, beta = 3