A proof by simplification works.
Simplification of the lhs term:
= by
Simplification of the rhs term:
![[Graphics:submitted.nbgr296.gif]](submitted.nbgr296.gif)
![[Graphics:submitted.nbgr297.gif]](submitted.nbgr297.gif)
![[Graphics:submitted.nbgr298.gif]](submitted.nbgr298.gif)
= by ![[Graphics:submitted.nbgr299.gif]](submitted.nbgr299.gif)
![[Graphics:submitted.nbgr300.gif]](submitted.nbgr300.gif)
= by ![[Graphics:submitted.nbgr301.gif]](submitted.nbgr301.gif)
![[Graphics:submitted.nbgr302.gif]](submitted.nbgr302.gif)
![[Graphics:submitted.nbgr303.gif]](submitted.nbgr303.gif)