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Metamath Proof Explorer

Theorem 3orass

Description: Associative law for triple disjunction. (Contributed by NM, 8-Apr-1994)

Ref Expression
Assertion 3orass ⊢ φ ∨ ψ ∨ χ ↔ φ ∨ ψ ∨ χ

Proof

Step Hyp Ref Expression
1 df-3or ⊢ φ ∨ ψ ∨ χ ↔ φ ∨ ψ ∨ χ
2 orass ⊢ φ ∨ ψ ∨ χ ↔ φ ∨ ψ ∨ χ
3 1 2 bitri ⊢ φ ∨ ψ ∨ χ ↔ φ ∨ ψ ∨ χ