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Mathematica Teacher's Edition

Built-in Functions

Mathematical Functions

Numerical Functions

IntegerPart

IntegerPart[x] gives the integer part of x.

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