Theorem pm2.81

Description: Theorem *2.81 of WhiteheadRussell p. 108. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.81	|- ( ( ps -> ( ch -> th ) ) -> ( ( ph \/ ps ) -> ( ( ph \/ ch ) -> ( ph \/ th ) ) ) )

Proof

Step	Hyp	Ref	Expression
1		orim2	|- ( ( ps -> ( ch -> th ) ) -> ( ( ph \/ ps ) -> ( ph \/ ( ch -> th ) ) ) )
2		pm2.76	|- ( ( ph \/ ( ch -> th ) ) -> ( ( ph \/ ch ) -> ( ph \/ th ) ) )
3	1 2	syl6	|- ( ( ps -> ( ch -> th ) ) -> ( ( ph \/ ps ) -> ( ( ph \/ ch ) -> ( ph \/ th ) ) ) )