Abstract Algebra: Using automorphisms, we define the semidirect product of two groups. We prove the group property and construct various examples, including the dihedral groups. As an application, we show that there exist only two isomorphism classes for groups of order 10 (actually 2p with p an odd prime).
U.Reddit course materials available at ureddit.com/class/23794/intro-to-group-theory Master list at mathdoctorbob.org/UReddit.html
Includes course on Group Theory (problems and solutions at website) and Ring Theory, and Field Theory. For Prerequisites on proofs and sets, see the Math Major Basics course.