# How to find the convolution of e^t and sin(2t)

1. Nov 14, 2009

### errordude

1. The problem statement, all variables and given/known data
Hi, can anyone help me to determine the convolution for the 2π periodic function f(t)=e^t and sin2t

2. Nov 14, 2009

### Staff: Mentor

Re: Convolution

Someone can probably help you but I doubt they will until you show some effort at working this for yourself.

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On helping with questions: Any and all assistance given to homework assignments or textbook style exercises should be given only after the questioner has shown some effort in solving the problem. If no attempt is made then the questioner should be asked to provide one before any assistance is given. Under no circumstances should complete solutions be provided to a questioner, whether or not an attempt has been made.​

3. Nov 15, 2009

### errordude

Re: Convolution

well i know how to write e^t as a 2π periodic fourier series but then what?

4. Nov 15, 2009

### Staff: Mentor

Re: Convolution

What's the definition of the convolution of two functions? When you posted this problem, you deleted sections 2 and 3 about Relevant equations and your efforts at solving the problem.

5. Nov 15, 2009

### sutupidmath

Re: Convolution

You don't need to use FOurier transforms for this problem. It is quite simple indeed, just go to the definition of the convolution of two functions, as was suggested here all along:

$$f\ast g=\int_0^tf(\alpha)g(t-\alpha)d\alpha$$

Now just substitute your functions instead of g and f. Hint: inside the integral i would let g(t-alfa)=e^(t-alfa), it makes the integration process easier. You know how to integrate, right?