Theorem 3eqtrri 2231

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 2226	. 2 |- A = C
4		3eqtri.3	. 2 |- C = D
5	3, 4	eqtr2i 2227	1 |- D = A

Syntax hints:   = wceq 1373

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 1470  ax-gen 1472  ax-4 1533  ax-17 1549  ax-ext 2187

This theorem depends on definitions:  df-bi 117  df-cleq 2198

This theorem is referenced by:  resindm  5001  dfdm2  5217  cofunex2g  6195  df1st2  6305  df2nd2  6306  enq0enq  7544  dfn2  9308  9p1e10  9506  0.999...  11832  pockthi  12681  sincosq3sgn  15300  sincosq4sgn  15301