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Description: One of the two equality axioms of standard predicate calculus, called reflexivity of equality. (The other one is stdpc7 1892.) 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 1818  . 2  
2  1  axgen 1536  1 
Colors of variables: wff set class 
Syntax hints: wal 1532 
This theorem is referenced by: cbv3ALT 1876 
This theorem was proved from axioms: ax1 7 ax2 8 ax3 9 axmp 10 ax5 1533 ax6 1534 axgen 1536 ax12o 1664 ax9 1684 ax4 1692 
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