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Mathematica Teacher's Edition

Built-in Functions

Mathematical Functions

Numerical Functions

FractionalPart

FractionalPart[x] gives the fractional part of x.

Mathematical function (see Section A.3.10).
FractionalPart[x], in effect, takes all digits to the right of the decimal point and drops the others.
Examples: FractionalPart[2.4]; FractionalPart[2.6]; FractionalPart[-2.4]; FractionalPart[-2.6].
FractionalPart[x] + IntegerPart[x] is always exactly x.
FractionalPart[x] yields a result when x is any numeric quantity, whether or not it is an explicit number.
Example: FractionalPart[Pi^2].
For exact numeric quantities, FractionalPart internally uses numerical approximations to establish its result.
See The Mathematica Book on the web: Section 3.2.2.
See also: IntegerPart, Mod.

Further Examples