Prove that where "e" is the group identity.
A proof on the corollary of the Lagrange's Theorem. It's |a| divides |G|. I just stated there that a part of the proof for the corollary is to note/recall that |<a>| = |a|. And i think i also have to show the proof for |<a>| = |a|, because maybe my classmates might ask. ;]