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Theorem 8p1e9 8828
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 8754 . 2  |-  9  =  ( 8  +  1 )
21eqcomi 2121 1  |-  ( 8  +  1 )  =  9
Colors of variables: wff set class
Syntax hints:    = wceq 1316  (class class class)co 5742   1c1 7589    + caddc 7591   8c8 8745   9c9 8746
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 1408  ax-gen 1410  ax-ext 2099
This theorem depends on definitions:  df-bi 116  df-cleq 2110  df-9 8754
This theorem is referenced by:  cos2bnd  11394
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