Theorem neleqtrrd 2449

Description: If a class is not an element of another class, it is also not an element of an equal class. Deduction form. (Contributed by David Moews, 1-May-2017.)

Hypotheses

Ref	Expression
neleqtrrd.1	|- (ph -> -. C e. B)
neleqtrrd.2	|- (ph -> A = B)

Assertion

Ref	Expression
neleqtrrd	|- (ph -> -. C e. A)

Proof of Theorem neleqtrrd

Step	Hyp	Ref	Expression
1		neleqtrrd.1	. 2 |- (ph -> -. C e. B)
2		neleqtrrd.2	. . 3 |- (ph -> A = B)
3	2	eleq2d 2420	. 2 |- (ph -> (C e. A <-> C e. B))
4	1, 3	mtbird 292	1 |- (ph -> -. C e. A)

Syntax hints:  -. wn 3   -> wi 4   = wceq 1642   e. wcel 1710

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-11 1746  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542  df-cleq 2346  df-clel 2349

This theorem is referenced by: (None)