Metamath Proof Explorer


Theorem oplem1

Description: A specialized lemma for set theory (ordered pair theorem). (Contributed by NM, 18-Oct-1995) (Proof shortened by Wolf Lammen, 8-Dec-2012)

Ref Expression
Hypotheses oplem1.1 φ ψ χ
oplem1.2 φ θ τ
oplem1.3 ψ θ
oplem1.4 χ θ τ
Assertion oplem1 φ ψ

Proof

Step Hyp Ref Expression
1 oplem1.1 φ ψ χ
2 oplem1.2 φ θ τ
3 oplem1.3 ψ θ
4 oplem1.4 χ θ τ
5 3 notbii ¬ ψ ¬ θ
6 1 ord φ ¬ ψ χ
7 5 6 syl5bir φ ¬ θ χ
8 2 ord φ ¬ θ τ
9 7 8 jcad φ ¬ θ χ τ
10 4 biimpar χ τ θ
11 9 10 syl6 φ ¬ θ θ
12 11 pm2.18d φ θ
13 12 3 sylibr φ ψ