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Section3.8Sage Exercises

¶These exercises are about becoming comfortable working with groups in Sage.

###### 1

Create the groups `CyclicPermutationGroup(8)` and `DihedralGroup(4)` and name these groups `C` and `D`, respectively. We will understand these constructions better shortly, but for now just understand that both objects you create are actually groups.

###### 2

Check that `C` and `D` have the same size by using the `.order()` method. Determine which group is abelian, and which is not, by using the `.is_abelian()` method.

###### 3

Use the `.cayley_table()` method to create the Cayley table for each group.

###### 4

Write a nicely formatted discussion identifying differences between the two groups that are discernible in properties of their Cayley tables. In other words, what is {\em different} about these two groups that you can “see” in the Cayley tables? (In the Sage notebook, a Shift-click on a blue bar will bring up a mini-word-processor, and you can use use dollar signs to embed mathematics formatted using TeX syntax.)

###### 5

For `C` locate the one subgroup of order \(4\text{.}\) The group `D` has three subgroups of order \(4\text{.}\) Select one of the three subgroups of `D` that has a different structure than the subgroup you obtained from `C`.

The `.subgroups()` method will give you a list of all of the subgroups to help you get started. A Cayley table will help you tell the difference between the two subgroups. What properties of these tables did you use to determine the difference in the structure of the subgroups?

###### 6

The `.subgroup(elt_list)` method of a group will create the smallest subgroup containing the specified elements of the group, when given the elements as a list `elt_list`. Use this command to discover the shortest list of elements necessary to recreate the subgroups you found in the previous exercise. The equality comparison, `==`, can be used to test if two subgroups are equal.