Theorem u1lem9ab 761

Description: Lemma used in study of orthoarguesian law.

Assertion

Ref	Expression
u1lem9ab	(a⊥ →1 b)⊥ ≤ (a →1 b)

Proof of Theorem u1lem9ab

Step	Hyp	Ref	Expression
1		u1lem9a 759	. 2 (a⊥ →1 b)⊥ ≤ a⊥
2		u1lem9b 760	. 2 a⊥ ≤ (a →1 b)
3	1, 2	letr 129	1 (a⊥ →1 b)⊥ ≤ (a →1 b)

Syntax hints:   ≤ wle 2  ^⊥ wn 4   →₁ wi1 13

This theorem is referenced by:  3vcom 795  oa3-u1 971  oa3-u2 972

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

This theorem depends on definitions:  df-a 39  df-i1 43  df-le1 122  df-le2 123

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