# SP20:Lecture 18 prep

In this lecture we'll continue defining operations on modular numbers; we'll show how to divide and exponentiate them.

Before lecture, try to give a definition for exponentiation of modular numbers in the same way we did for addition and multiplication in the last lecture. Check to see whether your definition gives a well-defined function (hint: it shouldn't).

Please come to lecture knowing the following definitions:

If is a number (e.g. a modular number), then we say is a multiplicative inverse of if (or in the case of modular numbers).
Definition: Unit
If is a number that has a multiplicative inverse, then is called a unit.