Theorem eqtr2 2257

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 2240	. 2 |- ( A = B <-> B = A )
2		eqtr 2256	. 2 |- ( ( B = A /\ A = C ) -> B = C )
3	1, 2	sylanb 284	1 |- ( ( A = B /\ A = C ) -> B = C )

This proof depends on syntax axioms:   -> wi 4   /\ wa 104   = wceq 1402

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-gen 1502  ax-4 1563  ax-17 1579  ax-ext 2220

This proof depends on definitions:  df-bi 117  df-cleq 2231

This theorem is used by:  eqvinc  2949  eqvincg  2950  moop2  4392  reusv3i  4605  relop  4930  f0rn0  5587  fliftfun  6002  th3qlem1  6911  enq0ref  7800  enq0tr  7801  genpdisj  7890  addlsub  8696  wrd2ind  11495  fsum2dlemstep  12201  0dvds  12578  cncongr1  12881  4sqlem12  13181  uhgr2edg  16447  usgredgreu  16457  uspgredg2vtxeu  16459