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Controlling Numerical Evaluation

NHoldAllprevent any arguments of a function from being affected by N
NHoldFirstprevent the first argument from being affected
NHoldRestprevent all but the first argument from being affected

Attributes for controlling numerical evaluation.

Usually N goes inside functions and gets applied to each of their arguments.
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This tells Mathematica not to apply N to the first argument of .
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Now the first argument of is left in its exact form.
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