Good basic isomorphism online tutorials

[helix999]

How the group of symmetries of the regular pentagram is isomorphic to the dihedral group of order 10?

Suggest me some good basic isomorphism online tutorial.

 

[Pere Callahan]

I suggest you go to your library and have a look at the books your teacher recommended.

If you want to get specific help I suggest you state the definitions of the mathematical terms involved and show what you have tried so far.