Theorem excomim

Description: One direction of Theorem 19.11 of Margaris p. 89. (Contributed by NM, 5-Aug-1993) (Revised by Mario Carneiro, 24-Sep-2016) Remove dependencies on ax-5 , ax-6 , ax-7 , ax-10 , ax-12 . (Revised by Wolf Lammen, 8-Jan-2018)

	Ref	Expression
Assertion	excomim	⊢ ( ∃ 𝑥 ∃ 𝑦 𝜑 → ∃ 𝑦 ∃ 𝑥 𝜑 )

Proof

Step	Hyp	Ref	Expression
1		excom	⊢ ( ∃ 𝑥 ∃ 𝑦 𝜑 ↔ ∃ 𝑦 ∃ 𝑥 𝜑 )
2	1	biimpi	⊢ ( ∃ 𝑥 ∃ 𝑦 𝜑 → ∃ 𝑦 ∃ 𝑥 𝜑 )