Theorem wa3 193

Description: Weak A3. (Contributed by NM, 27-Sep-1997.)

Assertion

Ref	Expression
wa3	(((a ∪ b) ∪ c) ≡ (a ∪ (b ∪ c))) = 1

Proof of Theorem wa3

Step	Hyp	Ref	Expression
1		ax-a3 32	. 2 ((a ∪ b) ∪ c) = (a ∪ (b ∪ c))
2	1	bi1 118	1 (((a ∪ b) ∪ c) ≡ (a ∪ (b ∪ c))) = 1

Syntax hints:   = wb 1   ≡ tb 5   ∪ wo 6  1wt 8

This theorem was proved from axioms:  ax-a1 30  ax-a2 31  ax-a3 32  ax-a5 34  ax-r1 35  ax-r2 36  ax-r4 37  ax-r5 38

This theorem depends on definitions:  df-b 39  df-a 40  df-t 41  df-f 42

This theorem is referenced by:  ska2  432