Metamath Proof Explorer


Theorem 3orel1

Description: Partial elimination of a triple disjunction by denial of a disjunct. (Contributed by Scott Fenton, 26-Mar-2011)

Ref Expression
Assertion 3orel1 ¬φφψχψχ

Proof

Step Hyp Ref Expression
1 3orass φψχφψχ
2 orel1 ¬φφψχψχ
3 1 2 syl5bi ¬φφψχψχ