The specific explanation is this:
Proof: (1)PVQ P
This is a known condition, not much explanation.
(2)┐P→Q T( 1)E
Show step (1) because PVQ
(3)Q→S P
This is a known condition, not much explanation.
(4)┐P→S T(2)(3)I
According to steps (2) and (3), ┐P→Q and ┐Q→S are transferred to obtain ┐ P→ S.
(5)┐S→P T(4)E
According to the conclusion of step (4), this is proved by theorem.
If the simple evidence is
┐P→S <= & gtPVS & lt= & gtSVP <= & gt┐S→P
(6)P→R P
This is a known condition, not much explanation.
(7)┐S→R Article 5, Paragraph 6, Item 1)
According to the conclusions of (5) and (6)
⑻SVR T(7)E
According to (7)- >, reapply; Expansion theorem.