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Theorem 8p1e9 8867
Description: 8 + 1 = 9. (Contributed by Mario Carneiro, 18-Apr-2015.)
Assertion
Ref Expression
8p1e9 (8 + 1) = 9

Proof of Theorem 8p1e9
StepHypRef Expression
1 df-9 8793 . 2 9 = (8 + 1)
21eqcomi 2143 1 (8 + 1) = 9
Colors of variables: wff set class
Syntax hints:   = wceq 1331  (class class class)co 5774  1c1 7628   + caddc 7630  8c8 8784  9c9 8785
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 1423  ax-gen 1425  ax-ext 2121
This theorem depends on definitions:  df-bi 116  df-cleq 2132  df-9 8793
This theorem is referenced by:  cos2bnd  11474
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