Metamath Proof Explorer


Theorem pm10.56

Description: Theorem *10.56 in WhiteheadRussell p. 156. (Contributed by Andrew Salmon, 24-May-2011)

Ref Expression
Assertion pm10.56 x φ ψ x φ χ x ψ χ

Proof

Step Hyp Ref Expression
1 pm3.45 φ ψ φ χ ψ χ
2 1 aleximi x φ ψ x φ χ x ψ χ
3 2 imp x φ ψ x φ χ x ψ χ