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Denominator

  • Denominator[ expr ] gives the denominator of expr.
  • Denominator picks out terms which have superficially negative exponents. Numerator picks out all 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 denominators.
  • Denominator can be used on rational numbers.
  • See the Mathematica book: Section 1.4.6.
  • See also: ExpandDenominator.

    Further Examples

    Here is a numerator and denominator.

    In[1]:=

    Out[1]=

    For trigonometric expressions, you need to use the Trig->True option.

    In[2]:=

    Out[2]=


    In[3]:=

    Out[3]=

    This gives the denominator over the integers modulo 3.

    In[4]:=

    Out[4]=