Theorem alsc2d 46498

Description: Deduction rule: Given "all some" applied to a class, you can extract the "there exists" part. (Contributed by David A. Wheeler, 20-Oct-2018.)

Hypothesis

Ref	Expression
alsc2d.1	⊢ (𝜑 → ∀!𝑥 ∈ 𝐴𝜓)

Assertion

Ref	Expression
alsc2d	⊢ (𝜑 → ∃𝑥 𝑥 ∈ 𝐴)

Proof of Theorem alsc2d

Step	Hyp	Ref	Expression
1		alsc2d.1	. . 3 ⊢ (𝜑 → ∀!𝑥 ∈ 𝐴𝜓)
2		df-alsc 46493	. . 3 ⊢ (∀!𝑥 ∈ 𝐴𝜓 ↔ (∀𝑥 ∈ 𝐴 𝜓 ∧ ∃𝑥 𝑥 ∈ 𝐴))
3	1, 2	sylib 217	. 2 ⊢ (𝜑 → (∀𝑥 ∈ 𝐴 𝜓 ∧ ∃𝑥 𝑥 ∈ 𝐴))
4	3	simprd 496	1 ⊢ (𝜑 → ∃𝑥 𝑥 ∈ 𝐴)

Syntax hints:   → wi 4   ∧ wa 396  ∃wex 1782   ∈ wcel 2106  ∀wral 3064  ∀!walsc 46491

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 206  df-an 397  df-alsc 46493

This theorem is referenced by:  alscn0d  46499