i am not sure if my computation is correct. Hope someone can have a look at it. Here is my problem:
I got to my solution by looking at a similar example.
But i don't know how they got rid of the sum.
i am not sure if my computation is correct. Hope someone can have a look at it. Here is my problem:
I got to my solution by looking at a similar example.
But i don't know how they got rid of the sum.
The summation is simply a geometric series. You remove the summation by using the formula
\begin{equation} 1+x+x^2 +\ldots = \frac{1}{1-x} \end{equation}
For the magnitude response, you just have to use your formula $|c|^2 = cc^*$. If $c = a+ib$, this gives you $|c| = \sqrt{a^2 + b^2}$.