Metamath Proof Explorer


Theorem frege13

Description: A closed form of com3r . Proposition 13 of Frege1879 p. 37. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)

Ref Expression
Assertion frege13 φ ψ χ θ χ φ ψ θ

Proof

Step Hyp Ref Expression
1 frege12 φ ψ χ θ φ χ ψ θ
2 frege12 φ ψ χ θ φ χ ψ θ φ ψ χ θ χ φ ψ θ
3 1 2 ax-mp φ ψ χ θ χ φ ψ θ