A proof by simplification works.
Simplification of the lhs term:
= by
Simplification of the rhs term:
![[Graphics:submitted.nbgr284.gif]](submitted.nbgr284.gif)
![[Graphics:submitted.nbgr285.gif]](submitted.nbgr285.gif)
![[Graphics:submitted.nbgr286.gif]](submitted.nbgr286.gif)
= by ![[Graphics:submitted.nbgr287.gif]](submitted.nbgr287.gif)
![[Graphics:submitted.nbgr288.gif]](submitted.nbgr288.gif)
![[Graphics:submitted.nbgr289.gif]](submitted.nbgr289.gif)