knows that constants such as Pi
are numeric quantities. It also knows that standard mathematical functions such as Log
have numerical values when their arguments are numerical.
In general, Mathematica
assumes that any function which has the attribute NumericFunction
will yield numerical values when its arguments are numerical. All standard mathematical functions in Mathematica
already have this attribute. But when you define your own functions, you can explicitly set the attribute to tell Mathematica
to assume that these functions will have numerical values when their arguments are numerical.