Theorem 3sstr4d 3201

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 3187	. 2 ⊢ (𝜑 → (𝐶 ⊆ 𝐷 ↔ 𝐴 ⊆ 𝐵))
5	1, 4	mpbird 167	1 ⊢ (𝜑 → 𝐶 ⊆ 𝐷)

Syntax hints:   → wi 4   = wceq 1353   ⊆ wss 3130

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-11 1506  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159

This theorem depends on definitions:  df-bi 117  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-in 3136  df-ss 3143

This theorem is referenced by:  rdgss  6384  sucinc2  6447  oawordi  6470  nnnninf  7124  fzoss1  10171  fzoss2  10172  clsss  13621  ntrss  13622  sslm  13750  txss12  13769  metss2lem  14000  xmettxlem  14012  xmettx  14013  nnsf  14757  nninfself  14765