Theorem 8p1e9 9018

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 8944	. 2 ⊢ 9 = (8 + 1)
2	1	eqcomi 2174	1 ⊢ (8 + 1) = 9

Syntax hints:   = wceq 1348  (class class class)co 5853  1c1 7775   + caddc 7777  8c8 8935  9c9 8936

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1440  ax-gen 1442  ax-ext 2152

This theorem depends on definitions:  df-bi 116  df-cleq 2163  df-9 8944

This theorem is referenced by:  cos2bnd  11723