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	$$⊢\exists x\exists y\phi \to \exists y\exists x\phi$$

Proof

Step	Hyp	Ref	Expression
1		excom	$$⊢\exists x\exists y\phi \leftrightarrow \exists y\exists x\phi$$
2	1	biimpi	$$⊢\exists x\exists y\phi \to \exists y\exists x\phi$$