Theorem 3eqtr2d 2391

Description: A deduction from three chained equalities. (Contributed by NM, 4-Aug-2006.)

Hypotheses

Ref	Expression
3eqtr2d.1	|- (ph -> A = B)
3eqtr2d.2	|- (ph -> C = B)
3eqtr2d.3	|- (ph -> C = D)

Assertion

Ref	Expression
3eqtr2d	|- (ph -> A = D)

Proof of Theorem 3eqtr2d

Step	Hyp	Ref	Expression
1		3eqtr2d.1	. . 3 |- (ph -> A = B)
2		3eqtr2d.2	. . 3 |- (ph -> C = B)
3	1, 2	eqtr4d 2388	. 2 |- (ph -> A = C)
4		3eqtr2d.3	. 2 |- (ph -> C = D)
5	3, 4	eqtrd 2385	1 |- (ph -> A = D)

Syntax hints:   -> wi 4   = wceq 1642

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-11 1746  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-ex 1542  df-cleq 2346

This theorem is referenced by: (None)