Theorem eqtr2 2212

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 2195	. 2 |- ( A = B <-> B = A )
2		eqtr 2211	. 2 |- ( ( B = A /\ A = C ) -> B = C )
3	1, 2	sylanb 284	1 |- ( ( A = B /\ A = C ) -> B = C )

Syntax hints:   -> wi 4   /\ wa 104   = wceq 1364

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-5 1458  ax-gen 1460  ax-4 1521  ax-17 1537  ax-ext 2175

This theorem depends on definitions:  df-bi 117  df-cleq 2186

This theorem is referenced by:  eqvinc  2884  eqvincg  2885  moop2  4281  reusv3i  4491  relop  4813  f0rn0  5449  fliftfun  5840  th3qlem1  6693  enq0ref  7495  enq0tr  7496  genpdisj  7585  addlsub  8391  fsum2dlemstep  11580  0dvds  11957  cncongr1  12244  4sqlem12  12543