Next, the real and imaginary sums must be examined to determine when the are equal to 0. These sums each regularly alternate between positive and negative terms due to the -1 in the numerator. However, further alternating can occur due to the sine and cosine functions. The portion of alternating due to the -1 can be separated by splitting the sums into their even and odd terms.
The task now is to determine when the positive portions of the even and odd sums cancel the negative portions, for both the real and imaginary sums.