P represents the known condition, and T( 1)E represents the result obtained from the conclusion of the previous step (1). E should be deduced according to the theorem, and I should be deduced according to the conclusion of the previous step or steps.

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.