Hi all,

My brain is fried by now, I'm not sure where to go with this homework problem.

Problem:

Prove that in iff (See problem 15.26).

Things that might come in handy:

Here is problem 15.26:

Prove that if , then in

For notation, see here

There's a theorem, I don't know how useful it would be in this case.

Theorem:Let and be subsets of a group . Then

iff and

I will supply any other useful information upon request.

What I tried:

Like i said, my brain is fried.

I'm not sure how to apply the part, but i know that, given that that's true, i want to show that , for

Also lost for the converse.

Thanks guys and gals