Theorem eqtr2 2251

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 2234	. 2 |- ( A = B <-> B = A )
2		eqtr 2250	. 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 1398

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 1496  ax-gen 1498  ax-4 1559  ax-17 1575  ax-ext 2214

This theorem depends on definitions:  df-bi 117  df-cleq 2225

This theorem is referenced by:  eqvinc  2940  eqvincg  2941  moop2  4368  reusv3i  4580  relop  4905  f0rn0  5562  fliftfun  5969  th3qlem1  6871  enq0ref  7748  enq0tr  7749  genpdisj  7838  addlsub  8643  wrd2ind  11415  fsum2dlemstep  12120  0dvds  12497  cncongr1  12800  4sqlem12  13100  uhgr2edg  16201  usgredgreu  16211  uspgredg2vtxeu  16213