Theorem sbequ8ALT 2148

Description: Alternate proof of sbequ8 1744, shorter but requiring more axioms. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.) (Proof modification is discouraged.)

Assertion

Ref	Expression
sbequ8ALT

Proof of Theorem sbequ8ALT

Step	Hyp	Ref	Expression
1		equsb1 2107	. . 3
2	1	a1bi 337	. 2
3		sbim 2136	. 2
4	2, 3	bitr4i 252	1

Syntax hints:  ->wi 4  <->wb 184  [wsb 1739

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1618  ax-4 1631  ax-5 1704  ax-6 1747  ax-7 1790  ax-10 1837  ax-12 1854  ax-13 1999

This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-ex 1613  df-nf 1617  df-sb 1740