Can't Seem to Solve Alpha: Find the Limit

[SherlockOhms]

See attached image.
Can't seem to get alpha to compute this. Had this in a test and it stumped me. Could someone explain how to find the limit? Thanks in advance guys.

 

[Snark1994]

Just divide top and bottom by n. Then the limit of the numerator is 1, while the limit of the denominator is 2i (the \frac{(-1)^n}{n} has magnitude which tends to 0).

 

[SherlockOhms]

Cool, thanks man. I was under impression that I had to separate the function up into it's real and imaginary parts.