Theorem pm13.18 2768

Description: Theorem *13.18 in [WhiteheadRussell] p. 178. (Contributed by Andrew Salmon, 3-Jun-2011.)

Assertion

Ref	Expression
pm13.18

Proof of Theorem pm13.18

Step	Hyp	Ref	Expression
1		eqeq1 2461	. . . 4
2	1	biimprd 223	. . 3
3	2	necon3d 2681	. 2
4	3	imp 429	1

Syntax hints:  ->wi 4  /\wa 369  =wceq 1395  =/=wne 2652

This theorem is referenced by:  pm13.181  2769  cncfiooicclem1  31696  4atexlemex4  35797

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1618  ax-4 1631  ax-ext 2435

This theorem depends on definitions:  df-bi 185  df-an 371  df-cleq 2449  df-ne 2654