Theorem 8p1e9 8884

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 8810	. 2 ⊢ 9 = (8 + 1)
2	1	eqcomi 2144	1 ⊢ (8 + 1) = 9

Syntax hints:   = wceq 1332  (class class class)co 5782  1c1 7645   + caddc 7647  8c8 8801  9c9 8802

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 1424  ax-gen 1426  ax-ext 2122

This theorem depends on definitions:  df-bi 116  df-cleq 2133  df-9 8810

This theorem is referenced by:  cos2bnd  11503