Numerator[expr]Numerator of a fraction:
Numerator[2 / 3]
Numerator of a symbolic fraction:
Numerator[a / b]
Numerator of a symbolic rational expression:
Numerator[(x - 1) (x - 2)/(x - 3)^2]
Numerator of a Gaussian rational:
Numerator[3/7 + I/11]
Numerators for the common trigonometric functions:
Numerator[{Sin[x], Cos[x], Tan[x], Csc[x], Sec[x], Cot[x]}, Trig -> True]
Numerators for the common hyperbolic functions:
Numerator[{Sinh[x], Cosh[x], Tanh[x], Csch[x], Sech[x], Coth[x]}, Trig -> True]
An expression is the quotient of its numerator and denominator:
expr = 5/7 (x - 1)^2/(x - 2)^3 a^b c^-d
num = Numerator[expr]
den = Denominator[expr]
expr === num / den
See also Denominator.