Metamath Proof Explorer


Theorem dmmptdff

Description: The domain of the mapping operation, deduction form. (Contributed by Glauco Siliprandi, 21-Dec-2024)

Ref Expression
Hypotheses dmmptdff.x 𝑥 𝜑
dmmptdff.1 𝑥 𝐵
dmmptdff.a 𝐴 = ( 𝑥𝐵𝐶 )
dmmptdff.c ( ( 𝜑𝑥𝐵 ) → 𝐶𝑉 )
Assertion dmmptdff ( 𝜑 → dom 𝐴 = 𝐵 )

Proof

Step Hyp Ref Expression
1 dmmptdff.x 𝑥 𝜑
2 dmmptdff.1 𝑥 𝐵
3 dmmptdff.a 𝐴 = ( 𝑥𝐵𝐶 )
4 dmmptdff.c ( ( 𝜑𝑥𝐵 ) → 𝐶𝑉 )
5 3 dmmpt dom 𝐴 = { 𝑥𝐵𝐶 ∈ V }
6 4 elexd ( ( 𝜑𝑥𝐵 ) → 𝐶 ∈ V )
7 1 6 ralrimia ( 𝜑 → ∀ 𝑥𝐵 𝐶 ∈ V )
8 2 rabid2f ( 𝐵 = { 𝑥𝐵𝐶 ∈ V } ↔ ∀ 𝑥𝐵 𝐶 ∈ V )
9 7 8 sylibr ( 𝜑𝐵 = { 𝑥𝐵𝐶 ∈ V } )
10 5 9 eqtr4id ( 𝜑 → dom 𝐴 = 𝐵 )