In non-standard analysis a whole set of infinitesinal numbers is introduced which are essentially zero. But you can do math with them (including division) and t

In non-standard analysis a whole set of infinitesinal numbers is introduced which are essentially zero. But you can do math with them (including division) and they are very useful for an alternative version of calculus. https://en.wikipedia.org/wiki/Nonstandard_analysis https://en.wikipedia.org/wiki/Nonstandard_analysis and https://en.wikipedia.org/wiki/Nonstandard_calculus https://en.wikipedia.org/wiki/Nonstandard_calculus