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Description: One of the two equality axioms of standard predicate calculus, called reflexivity of equality. (The other one is stdpc7 1859.) Axiom 6 of [Mendelson] p. 95. Mendelson doesn't say why he prepended the redundant quantifier, but it was probably to be compatible with free logic (which is valid in the empty domain). (Contributed by NM, 16Feb2005.) 
Ref  Expression 

stdpc6 
Step  Hyp  Ref  Expression 

1  equid 1646  . 2  
2  1  axgen 1534  1 
Colors of variables: wff set class 
Syntax hints: wal 1528 
This theorem is referenced by: cbv3h 1925 
This theorem was proved from axioms: ax1 7 ax2 8 ax3 9 axmp 10 axgen 1534 ax5 1545 ax17 1604 ax9 1637 ax8 1645 
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