I have another question.
How to show that ?
, , , be four subgroups of a group with and .
Let .
I have shown the following:
(1)
(2)
(3)
(4)
If , then for and ;
define by .
I'm facing problem to show that is well-defined.
I started with ;
implies that . ----------( )
I'm stuck here.
I know I need to get ; ------------( )
implies that ;
finally .
How to continue from ( ) to ( )?