Theorem eqtr2 2250

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 2233	. 2 |- ( A = B <-> B = A )
2		eqtr 2249	. 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 2213

This theorem depends on definitions:  df-bi 117  df-cleq 2224

This theorem is referenced by:  eqvinc  2930  eqvincg  2931  moop2  4350  reusv3i  4562  relop  4886  f0rn0  5540  fliftfun  5947  th3qlem1  6849  enq0ref  7713  enq0tr  7714  genpdisj  7803  addlsub  8608  wrd2ind  11370  fsum2dlemstep  12075  0dvds  12452  cncongr1  12755  4sqlem12  13055  uhgr2edg  16147  usgredgreu  16157  uspgredg2vtxeu  16159