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based on an earlier version of the Wolfram Language.
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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:
In[1]:=
Click for copyable input
Out[1]=
Extract the numerator of a rational expression:
In[2]:=
Click for copyable input
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:
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