Here we begin our study of group theory topics.
Lagrange's Theorem. The order of a subgroup of a finite group divides the order of the group.
Internal semidirect products. One way to factor a group is by the direct product
of two of its subgroups, when that is possible. An alternative way to factor a
group is by the inner semidirect product of two subgroups.
Inner semidirect products by extensions. This is a read-along set of notes on the
presentation in the YouTube video by Martin Baker on the topic.