Numerator

Numerator[expr]

gives the numerator of expr.

Details and Options

  • Numerator picks out terms which do not have superficially negative exponents. Denominator picks out the remaining terms.
  • An exponent is "superficially negative" if it has a negative number as a factor.
  • The standard representation of rational expressions as products of powers means that you cannot simply use Part to extract numerators.
  • Numerator can be used on rational numbers.

Examples

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Basic Examples  (1)

Extract the numerator of a rational number:

Extract the numerator of a rational expression:

Scope  (7)

Rational numbers:

Gaussian rationals:

Rational expressions:

Select terms without syntactically negative exponents:

All exponents syntactically negative:

No syntactically negative exponents:

Numerator automatically threads over lists:

Options  (2)

Modulus  (1)

Find numerators over integers modulo :

Trig  (1)

Numerators of trigonometric functions:

Properties & Relations  (4)

Denominator gives the terms with negative exponents:

An expression is a quotient of its numerator and denominator:

Use Cancel to cancel common factors between the numerator and the denominator:

Together writes an expression as a fraction and cancels common terms:

Introduced in 1988
 (1.0)