Theorem 3sstr4d 3187

Description: Substitution of equality into both sides of a subclass relationship. (Contributed by NM, 30-Nov-1995.) (Proof shortened by Eric Schmidt, 26-Jan-2007.)

Hypotheses

Ref	Expression
3sstr4d.1	⊢ (𝜑 → 𝐴 ⊆ 𝐵)
3sstr4d.2	⊢ (𝜑 → 𝐶 = 𝐴)
3sstr4d.3	⊢ (𝜑 → 𝐷 = 𝐵)

Assertion

Ref	Expression
3sstr4d	⊢ (𝜑 → 𝐶 ⊆ 𝐷)

Proof of Theorem 3sstr4d

Step	Hyp	Ref	Expression
1		3sstr4d.1	. 2 ⊢ (𝜑 → 𝐴 ⊆ 𝐵)
2		3sstr4d.2	. . 3 ⊢ (𝜑 → 𝐶 = 𝐴)
3		3sstr4d.3	. . 3 ⊢ (𝜑 → 𝐷 = 𝐵)
4	2, 3	sseq12d 3173	. 2 ⊢ (𝜑 → (𝐶 ⊆ 𝐷 ↔ 𝐴 ⊆ 𝐵))
5	1, 4	mpbird 166	1 ⊢ (𝜑 → 𝐶 ⊆ 𝐷)

Syntax hints:   → wi 4   = wceq 1343   ⊆ wss 3116

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-11 1494  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-nf 1449  df-sb 1751  df-clab 2152  df-cleq 2158  df-clel 2161  df-in 3122  df-ss 3129

This theorem is referenced by:  rdgss  6351  sucinc2  6414  oawordi  6437  nnnninf  7090  fzoss1  10106  fzoss2  10107  clsss  12758  ntrss  12759  sslm  12887  txss12  12906  metss2lem  13137  xmettxlem  13149  xmettx  13150  nnsf  13885  nninfself  13893