Metamath Proof Explorer


Theorem frege20

Description: A closed form of syl8 . Proposition 20 of Frege1879 p. 40. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)

Ref Expression
Assertion frege20 φ ψ χ θ θ τ φ ψ χ τ

Proof

Step Hyp Ref Expression
1 frege19 ψ χ θ θ τ ψ χ τ
2 frege18 ψ χ θ θ τ ψ χ τ φ ψ χ θ θ τ φ ψ χ τ
3 1 2 ax-mp φ ψ χ θ θ τ φ ψ χ τ