Denominator of a rational expression
This functionality does not run in MATLAB.
denom(f) returns the denominator of the expression f.
denom regards the input as a rational expression: non-rational subexpressions such as sin(x), x^(1/2) etc. are internally replaced by "temporary variables". The denominator of this rationalized expression is computed, the temporary variables are finally replaced by the original subexpressions.
We compute the denominators of some expressions:
denom(x + 1/(2/3*x -2/x))
denom((cos(x)^2 -1)/(cos(x) -1))
denom performs no cancellations if the rational expression is of the form "numerator/denominator":
r := (x^2 - 1)/(x^3 - x^2 + x - 1): denom(r)
This denominator has a common factor with the numerator of r; normal enforces cancellation of common factors:
However, automatic normalization occurs if the input expression is a sum:
denom(r + x/(x + 1) + 1/(x + 1) - 1)