Infinity, like dividing by zero, sometimes works.
It's like if you have a large crowd of people. You ask a question to X, and sometimes X answers, and sometimes Y answers. If you can rely on X answering, than 0/0 is the same as X/X, is quite definite.
Sometimes, you can tell that Y and X are related by a common mantissa or modulus, and therefore you can use some information, but not exactly.
Sometimes, you can replace an infinite sum that goes nowhere by another property that goes somewhere.
Infinity does not just "happen", but has an "onset" of loss of information.
Split from "Forum inactivity" ~Keiji