Theorem eqtr2 2189

Description: A transitive law for class equality. (Contributed by NM, 20-May-2005.) (Proof shortened by Andrew Salmon, 25-May-2011.)

Assertion

Ref	Expression
eqtr2	|- ( ( A = B /\ A = C ) -> B = C )

Proof of Theorem eqtr2

Step	Hyp	Ref	Expression
1		eqcom 2172	. 2 |- ( A = B <-> B = A )
2		eqtr 2188	. 2 |- ( ( B = A /\ A = C ) -> B = C )
3	1, 2	sylanb 282	1 |- ( ( A = B /\ A = C ) -> B = C )

Syntax hints:   -> wi 4   /\ wa 103   = wceq 1348

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1440  ax-gen 1442  ax-4 1503  ax-17 1519  ax-ext 2152

This theorem depends on definitions:  df-bi 116  df-cleq 2163

This theorem is referenced by:  eqvinc  2853  eqvincg  2854  moop2  4236  reusv3i  4444  relop  4761  f0rn0  5392  fliftfun  5775  th3qlem1  6615  enq0ref  7395  enq0tr  7396  genpdisj  7485  addlsub  8289  fsum2dlemstep  11397  0dvds  11773  cncongr1  12057