Edited: Making the question as brief as possible to avoid future confusion and misunderstanding.
Note
This was moved as a separate question from: Product of all real numbers in a given interval $[n,m]$
Since it was a part of it that wasn't getting any attention.
Question
How would one calculate the infinite product of negative numbers? For example, in this case:
$$-1\times -1\times-1\times -1\dots=$$
Or is the result of this series simply undefined?
The value of $\lim\limits_{n\to\infty}(-1)^n$ is undefined.