represents an infinite numerical quantity whose direction in the complex plane is unknown.
represents an infinite numerical quantity that is a positive real multiple of the complex number z.
DirectedInfinity
represents an infinite numerical quantity whose direction in the complex plane is unknown.
represents an infinite numerical quantity that is a positive real multiple of the complex number z.
Details
- You can think of DirectedInfinity[z] as representing a point in the complex plane reached by starting at the origin and going an infinite distance in the direction of the point z.
- The following conversions are made:
-
Infinity DirectedInfinity[1] -Infinity DirectedInfinity[-1] ComplexInfinity DirectedInfinity[] - Certain arithmetic operations are performed on DirectedInfinity quantities.
- In OutputForm, DirectedInfinity[z] is printed in terms of Infinity, and DirectedInfinity[] is printed as ComplexInfinity.
Examples
open all close allBasic Examples (3)
Scope (6)
Some directions have a special StandardForm:
Table[DirectedInfinity[i], {i, {1, -1, I, -I}}]Limit[1 / x, x -> ∞]Use Infinity as an alternative input form:
Infinity//FullFormMultiplying by a number changes the direction:
(1 + I) InfinityUnspecified or Indeterminate direction represents ComplexInfinity:
{DirectedInfinity[], DirectedInfinity[Indeterminate]}Finite or symbolic quantities are absorbed:
3 DirectedInfinity[z]I DirectedInfinity[z]DirectedInfinity[z] + xExtended arithmetic with infinite quantities:
DirectedInfinity[x] DirectedInfinity[y]DirectedInfinity[x] + DirectedInfinity[y]In this case the result depends on the directions x and y:
DirectedInfinity[x] + DirectedInfinity[y] /. {x -> 1, y -> 2}DirectedInfinity[x] + DirectedInfinity[y] /. {x -> 1, y -> -1}Operations that cannot be unambiguously defined produce Indeterminate:
DirectedInfinity[x] / DirectedInfinity[y]In this case the result depends on the growth rates of the numerator and denominator:
Limit[(x t) / (y t ^ 2), t -> Infinity]Limit[(x t) / (y (t + 1)), t -> Infinity]Use in mathematical functions:
Sin[DirectedInfinity[]]BesselJ[0, -Infinity]The value in different directions may vary:
{Exp[Infinity], Exp[-Infinity]}Applications (2)
Integrate along a line from the origin with direction
:
Integrate[Exp[-x ^ 2] / (x ^ 2 - 1), {x, 0, DirectedInfinity[Exp[I Pi / 4]]}]Asymptotics of the LogGamma function at DirectedInfinity[z]:
Series[LogGamma[n], {n, DirectedInfinity[z], 3}]Plot asymptotic value compared to function value in different directions:
Plot[Evaluate[Abs[Normal[%] - LogGamma[n]] /. {n -> 121 / 3z} /. z -> Exp[I ϕ]], {ϕ, -3, 3}]Properties & Relations (3)
Simplify and FullSimplify can generate infinities:
Simplify[1 / ((E + 1) ^ 2 - (E ^ 2 + 2E + 1))]FullSimplify[Log[Sin[Pi / 16] - Sqrt[2 - Sqrt[2 + Sqrt[2]]] / 2]]A nested DirectedInfinity reduces to one DirectedInfinity:
DirectedInfinity[DirectedInfinity[DirectedInfinity[I]]]DirectedInfinity[] is not a number:
NumberQ[DirectedInfinity[]]Possible Issues (3)
Symbolic quantities might get lost in operations:
DirectedInfinity[z] + xThe Accuracy and Precision for DirectedInfinity refer to the direction argument:
Precision[DirectedInfinity[Exp[I Pi / 4]]]Precision[DirectedInfinity[N[Exp[I Pi / 4], 20]]]Simplifications performed by the Wolfram Language assume symbols to represent numbers:
x / x∞ / ∞Tech Notes
Related Guides
Related Links
History
Introduced in 1988 (1.0)
Text
Wolfram Research (1988), DirectedInfinity, Wolfram Language function, https://reference.wolfram.com/language/ref/DirectedInfinity.html.
CMS
Wolfram Language. 1988. "DirectedInfinity." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/DirectedInfinity.html.
APA
Wolfram Language. (1988). DirectedInfinity. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/DirectedInfinity.html
BibTeX
@misc{reference.wolfram_2026_directedinfinity, author="Wolfram Research", title="{DirectedInfinity}", year="1988", howpublished="\url{https://reference.wolfram.com/language/ref/DirectedInfinity.html}", note=[Accessed: 13-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_directedinfinity, organization={Wolfram Research}, title={DirectedInfinity}, year={1988}, url={https://reference.wolfram.com/language/ref/DirectedInfinity.html}, note=[Accessed: 13-June-2026]}