- #1

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_{n=0}

^{∞}(-1)

^{n}=.5. However, in calculus, lim

_{n→∞}(-1)

^{n}=undefined. The limit does not exist. It is not 0, the average of -1 and 1 which are the only values of the function (if the domain is only integers). Yet, there must be some sense in it as it is used in string theory. Can somebody please explain this. Thanks!