Theorem dfss3f 3925

Description: Equivalence for subclass relation, using bound-variable hypotheses instead of distinct variable conditions. (Contributed by NM, 20-Mar-2004.)

Hypotheses

Ref	Expression
dfssf.1	⊢ Ⅎ𝑥𝐴
dfssf.2	⊢ Ⅎ𝑥𝐵

Assertion

Ref	Expression
dfss3f	⊢ (𝐴 ⊆ 𝐵 ↔ ∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐵)

Proof of Theorem dfss3f

Step	Hyp	Ref	Expression
1		dfssf.1	. . 3 ⊢ Ⅎ𝑥𝐴
2		dfssf.2	. . 3 ⊢ Ⅎ𝑥𝐵
3	1, 2	dfssf 3924	. 2 ⊢ (𝐴 ⊆ 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵))
4		df-ral 3052	. 2 ⊢ (∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵))
5	3, 4	bitr4i 278	1 ⊢ (𝐴 ⊆ 𝐵 ↔ ∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐵)

Syntax hints:   → wi 4   ↔ wb 206  ∀wal 1539   ∈ wcel 2113  Ⅎwnfc 2883  ∀wral 3051   ⊆ wss 3901

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968  ax-7 2009  ax-8 2115  ax-11 2162  ax-12 2184

This theorem depends on definitions:  df-bi 207  df-an 396  df-ex 1781  df-nf 1785  df-clel 2811  df-nfc 2885  df-ral 3052  df-ss 3918

This theorem is referenced by:  nfss  3926  nfchnd  18534  sigaclcu2  34277  bnj1498  35217  heibor1  38011  ssrabf  45358  ssrab2f  45361  limsupequzmpt2  45962  liminfequzmpt2  46035  pimconstlt1  46946  pimltpnff  46947  pimdecfgtioc  46959  pimincfltioc  46960  pimdecfgtioo  46961  pimincfltioo  46962  pimgtmnff  46966  sssmf  46982