Theorem sbexi 38073

Description: Discard class substitution in an existential quantification when substituting the quantified variable, in inference form. (Contributed by Giovanni Mascellani, 27-May-2019.)

Hypothesis

Ref	Expression
sbexi.1	⊢ 𝐴 ∈ V

Assertion

Ref	Expression
sbexi	⊢ ([𝐴 / 𝑥]∃𝑥𝜑 ↔ ∃𝑥𝜑)

Proof of Theorem sbexi

Step	Hyp	Ref	Expression
1		sbexi.1	. 2 ⊢ 𝐴 ∈ V
2		nfe1 2151	. 2 ⊢ Ⅎ𝑥∃𝑥𝜑
3	1, 2	sbcgfi 3885	1 ⊢ ([𝐴 / 𝑥]∃𝑥𝜑 ↔ ∃𝑥𝜑)

Syntax hints:   ↔ wb 206  ∃wex 1777   ∈ wcel 2108  Vcvv 3488  [wsbc 3804

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1793  ax-4 1807  ax-5 1909  ax-6 1967  ax-7 2007  ax-8 2110  ax-9 2118  ax-10 2141  ax-12 2178  ax-ext 2711

This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1540  df-ex 1778  df-nf 1782  df-sb 2065  df-clab 2718  df-cleq 2732  df-clel 2819  df-sbc 3805

This theorem is referenced by: (None)