Theorem elequ1 2152

Description: An identity law for the non-logical predicate. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
elequ1	|- ( x = y -> ( x e. z <-> y e. z ) )

Proof of Theorem elequ1

Step	Hyp	Ref	Expression
1		ax-13 2150	. 2 |- ( x = y -> ( x e. z -> y e. z ) )
2		ax-13 2150	. . 3 |- ( y = x -> ( y e. z -> x e. z ) )
3	2	equcoms 1708	. 2 |- ( x = y -> ( y e. z -> x e. z ) )
4	1, 3	impbid 129	1 |- ( x = y -> ( x e. z <-> y e. z ) )

Syntax hints:   -> wi 4   <-> wb 105

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-gen 1449  ax-ie2 1494  ax-8 1504  ax-17 1526  ax-i9 1530  ax-13 2150

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  cleljust  2154  elsb1  2155  dveel1  2157  nalset  4132  zfpow  4174  mss  4225  zfun  4433  ctssdc  7109  acfun  7203  ccfunen  7260  bj-nalset  14507  bj-nnelirr  14565  nninfsellemqall  14624  nninfomni  14628