Theorem 3sstr3d 3314

Description: Substitution of equality into both sides of a subclass relationship. (Contributed by NM, 1-Oct-2000.)

Hypotheses

Ref	Expression
3sstr3d.1	|- (ph -> A C_ B)
3sstr3d.2	|- (ph -> A = C)
3sstr3d.3	|- (ph -> B = D)

Assertion

Ref	Expression
3sstr3d	|- (ph -> C C_ D)

Proof of Theorem 3sstr3d

Step	Hyp	Ref	Expression
1		3sstr3d.1	. 2 |- (ph -> A C_ B)
2		3sstr3d.2	. . 3 |- (ph -> A = C)
3		3sstr3d.3	. . 3 |- (ph -> B = D)
4	2, 3	sseq12d 3301	. 2 |- (ph -> (A C_ B <-> C C_ D))
5	1, 4	mpbid 201	1 |- (ph -> C C_ D)

Syntax hints:   -> wi 4   = wceq 1642   C_ wss 3258

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-v 2862  df-nin 3212  df-compl 3213  df-in 3214  df-ss 3260

This theorem is referenced by: (None)