Theorem a16gALT 2049

Description: A generalization of Axiom ax-16 2144. Alternate proof of a16g 1945 that uses df-sb 1649. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
a16gALT	|- (A.x x = y -> (ph -> A.zph))

Distinct variable group:   x,y

Allowed substitution hints:   ph(x,y,z)

Proof of Theorem a16gALT

Step	Hyp	Ref	Expression
1		aev 1991	. 2 |- (A.x x = y -> A.z z = x)
2		ax16ALT2 2048	. 2 |- (A.x x = y -> (ph -> A.xph))
3		biidd 228	. . . 4 |- (A.z z = x -> (ph <-> ph))
4	3	dral1 1965	. . 3 |- (A.z z = x -> (A.zph <-> A.xph))
5	4	biimprd 214	. 2 |- (A.z z = x -> (A.xph -> A.zph))
6	1, 2, 5	sylsyld 52	1 |- (A.x x = y -> (ph -> A.zph))

Syntax hints:   -> wi 4  A.wal 1540

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-6 1729  ax-7 1734  ax-11 1746  ax-12 1925

This theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649

This theorem is referenced by: (None)