Continuing where Daniel left of with a discussions of groups of order 5.
A group with a prime order has certain qualities that are useful to know in figuring out its Cayley (multiplication) table. Most importantly, a prime group is always cyclic (can be generate by a single element and is abelian). This makes our job of filling out a Cayley table slightly easier. Let's start with our basic table, and fill out everything we know automatically.
- I have changed the notation slightly to emphasize that this is a group with a being the generating element with a5=e.
* | e | a1 | a2 | a3 | a4 |
e | e | a1 | a2 | a3 | a4 |
a1 | a1 | ||||
a2 | a2 | ||||
a3 | a3 | ||||
a4 | a4 |
Now we know that elements can only appear once in a row and column and remembering that a^5=e, we can fill out the table as such:
* | e | a1 | a2 | a3 | a4 |
e | e | a1 | a2 | a3 | a4 |
a1 | a1 | e | |||
a2 | a2 | e | |||
a3 | a3 | e | |||
a4 | a4 | e |
and then subsequently,
* | e | a1 | a2 | a3 | a4 |
e | e | a1 | a2 | a3 | a4 |
a1 | a1 | a2 | a3 | a4 | e |
a2 | a2 | a3 | a4 | e | a1 |
a3 | a3 | a4 | e | a1 | a2 |
a4 | a4 | e | a1 | a2 | a3 |