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BUILT-IN MATHEMATICA SYMBOL

Numerator

Numerator[expr]
gives the numerator of expr.

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.

Extract the numerator of a rational number:

Extract the numerator of a rational expression:

Extract the numerator of a rational number:

Out[1]=

Extract the numerator of a rational expression:

Out[2]=

Rational numbers:

Rational expressions:

Select terms without syntactically negative exponents:

All exponents syntactically negative:

No syntactically negative exponents:

Numerator automatically threads over lists:

Find numerators over integers modulo

Numerators of trigonometric functions:

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: