Theorem 3eqtrri 2120

Description: An inference from three chained equalities. (Contributed by NM, 3-Aug-2006.) (Proof shortened by Andrew Salmon, 25-May-2011.)

Hypotheses

Ref	Expression
3eqtri.1	|- A = B
3eqtri.2	|- B = C
3eqtri.3	|- C = D

Assertion

Ref	Expression
3eqtrri	|- D = A

Proof of Theorem 3eqtrri

Step	Hyp	Ref	Expression
1		3eqtri.1	. . 3 |- A = B
2		3eqtri.2	. . 3 |- B = C
3	1, 2	eqtri 2115	. 2 |- A = C
4		3eqtri.3	. 2 |- C = D
5	3, 4	eqtr2i 2116	1 |- D = A

Syntax hints:   = wceq 1296

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1388  ax-gen 1390  ax-4 1452  ax-17 1471  ax-ext 2077

This theorem depends on definitions:  df-bi 116  df-cleq 2088

This theorem is referenced by:  resindm  4787  dfdm2  4999  cofunex2g  5921  df1st2  6022  df2nd2  6023  enq0enq  7087  dfn2  8784  9p1e10  8978  0.999...  11064