Theorem wcon1 207

Description: Weak contraposition.

Hypothesis

Ref	Expression
wcon1.1	(a' == b') = 1

Assertion

Ref	Expression
wcon1	(a == b) = 1

Proof of Theorem wcon1

Step	Hyp	Ref	Expression
1		conb 122	. 2 (a == b) = (a' == b')
2		wcon1.1	. 2 (a' == b') = 1
3	1, 2	ax-r2 36	1 (a == b) = 1

Syntax hints:   = wb 1  'wn 4   == tb 5  1wt 8

This theorem is referenced by:  wcon3 209  wfh3 425  wfh4 426

This theorem was proved from axioms:  ax-a1 30  ax-a2 31  ax-r1 35  ax-r2 36  ax-r4 37  ax-r5 38

This theorem depends on definitions:  df-b 39  df-a 40

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