Theorem eqtr2 2184

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 2167	. 2 |- ( A = B <-> B = A )
2		eqtr 2183	. 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 1343

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 1435  ax-gen 1437  ax-4 1498  ax-17 1514  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-cleq 2158

This theorem is referenced by:  eqvinc  2849  eqvincg  2850  moop2  4229  reusv3i  4437  relop  4754  f0rn0  5382  fliftfun  5764  th3qlem1  6603  enq0ref  7374  enq0tr  7375  genpdisj  7464  addlsub  8268  fsum2dlemstep  11375  0dvds  11751  cncongr1  12035