For proving , by , it suffices to prove
.
We prove the individual conjunctive parts of :
Proof of :
Formula is simplified to
.
For proving , by , it suffices to prove
.
From by specialization we obtain
.
From by specialization we obtain
.
We prove first
.
We prove the individual conjunctive parts of :
From and we obtain by modus ponens
Proof of :
Formula is true because it is identical to .