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
.