Theorem 8p1e9 9445

Description: 8 + 1 = 9. (Contributed by Mario Carneiro, 18-Apr-2015.)

Assertion

Ref	Expression
8p1e9	|- ( 8 + 1 ) = 9

Proof of Theorem 8p1e9

Step	Hyp	Ref	Expression
1		df-9 9370	. 2 |- 9 = ( 8 + 1 )
2	1	eqcomi 2242	1 |- ( 8 + 1 ) = 9

This proof depends on syntax axioms:   = wceq 1402  (class class class)co 6085   1c1 8180   + caddc 8182   8c8 9361   9c9 9362

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-gen 1502  ax-ext 2220

This proof depends on definitions:  df-bi 117  df-cleq 2231  df-9 9370

This theorem is used by:  cos2bnd  12527  log2ublog2  16086