# Thread: I don't get it

1. ## I don't get it

I don't know how to find out the taylor series of exp(x)*cos(x)
I think I should write the taylor series for exp(x) and cos(x) separately and the multiply them, but I don't know how to multiply these two sums

2. ## Re: I don't get it

Originally Posted by andrei1293
I don't know how to find out the taylor series of exp(x)*cos(x)
Assuming the series at $x=0$ we get $\sum\limits_{n = o}^\infty {\frac{{{f^{(n)}}(0)}}{{n!}}x^n}$