Theorem u1lem1 716

Description: Lemma for unified implication study.

Assertion

Ref	Expression
u1lem1	((a ->1 b) ->1 a) = a

Proof of Theorem u1lem1

Step	Hyp	Ref	Expression
1		u1lemc1 662	. . . 4 a C (a ->1 b)
2	1	comcom 435	. . 3 (a ->1 b) C a
3	2	u1lemc4 683	. 2 ((a ->1 b) ->1 a) = ((a ->1 b)_|_ v a)
4		u1lemnoa 642	. 2 ((a ->1 b)_|_ v a) = a
5	3, 4	ax-r2 35	1 ((a ->1 b) ->1 a) = a

Syntax hints:   = wb 1  _|_wn 4   v wo 6   ->1 wi1 13

This theorem is referenced by:  u1lem1n 721  u1lem2 726

This theorem was proved from axioms:  ax-a1 29  ax-a2 30  ax-a3 31  ax-a4 32  ax-a5 33  ax-r1 34  ax-r2 35  ax-r4 36  ax-r5 37  ax-r3 421

This theorem depends on definitions:  df-b 38  df-a 39  df-t 40  df-f 41  df-i1 43  df-le1 122  df-le2 123  df-c1 124  df-c2 125

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