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Arg [z]

gives the argument of the complex number z.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Numerical Evaluation  
Specific Values  
Visualization  
Function Properties  
Function Identities and Simplifications  
Applications  
Properties & Relations  
Possible Issues  
Neat Examples  
See Also
Tech Notes
Related Guides
Related Links
History
Cite this Page

Arg [z]

gives the argument of the complex number z.

Details

  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • Arg [z] is left unevaluated if z is not a numeric quantity.
  • Arg [z] gives the phase angle of z in radians.
  • The result from Arg [z] is always between and .
  • Arg [z] has a branch cut discontinuity in the complex z plane running from to 0.
  • Arg [0] gives 0.
  • Arg automatically threads over lists. »
  • Arg can be used with Interval and CenteredInterval objects. »

Examples

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Basic Examples  (3)

The result is given in radians:

Plot over a subset of the reals:

Plot over a subset of the complexes:

Scope  (33)

Numerical Evaluation  (6)

Evaluate numerically:

Complex number inputs:

Evaluate to high precision:

For real inputs, the result is exact:

For complex inputs, the precision of the output tracks the precision of the input:

Evaluate efficiently at high precision:

Compute the elementwise values of an array using automatic threading:

Or compute the matrix Arg function using MatrixFunction :

Arg can be used with Interval and CenteredInterval objects:

Or compute average-case statistical intervals using Around :

Specific Values  (6)

Values of Arg at fixed points:

Value at zero:

Values at infinity:

Exact inputs:

Evaluate for complex exponentials:

Find a value of x for which the Arg [I x]=π/2:

Visualize the result:

Visualization  (5)

Plot the on the real axis:

Plot on the reals:

Plot over the complex plane:

Visualize Arg in three dimensions:

Use Arg to specify regions of the complex plane:

Function Properties  (11)

Arg is defined for all real and complex inputs:

Function range of Arg for real inputs:

Except on the negative reals, arg(TemplateBox[{z}, Conjugate])=-arg(z):

Arg is not a differentiable function:

The difference quotient does not have a limit in the complex plane:

There is only a limit in certain directions, for example, the real direction:

Use ComplexExpand to get differentiable expressions for real-valued variables:

Arg is not an analytic function:

It has both singularities and discontinuities:

Over the complex plane, it is singular everywhere and discontinuous on the non-positive reals:

Arg is nonincreasing:

Arg is not injective:

Arg is not surjective:

Arg is non-negative:

Arg is neither convex nor concave:

TraditionalForm formatting:

Function Identities and Simplifications  (5)

Expand assuming real variables x and y:

Simplify Abs using appropriate assumptions:

Express a non-zero complex number in term of its Arg and Abs :

is equal to :

Except for , exp(ⅈ arg(z))=TemplateBox[{z}, Sign]):

Applications  (3)

Polar decomposition of a complex number:

Color a plot according to value of Arg :

Expand multivalued functions without making assumptions about variables:

Properties & Relations  (7)

Simplify expressions containing Arg :

Generate Arg from FullSimplify :

Use Arg as a target function in ComplexExpand :

Rescale Arg to run from 0 to 1:

Find the domain of positivity for a linear function:

Use Arg to specify assumptions about complex variables:

ComplexPlot plots the phase of a function using color and shades by the magnitude:

Possible Issues  (4)

Degenerate cases give intervals as results:

Arg is a function of a complex variable and is therefore not differentiable:

As a complex function, it is not possible to write Arg [z] without involving Conjugate [z]:

In particular, the limit that defines the derivative is direction dependent and therefore does not exist:

Use ComplexExpand to get differentiable expressions for real-valued variables:

Numerical decision procedures with default settings cannot simplify this expression:

The machine-precision result is incorrect:

The arbitrary-precision result indicates that the result may be incorrect:

Using a larger setting for $MaxExtraPrecision gives the correct result:

The input contains a hidden zero, and simplifying the argument gets the correct answer:

The argument principle of complex analysis cannot be used because Arg has range :

Neat Examples  (1)

See Also

ArcTan   Sign   Abs   AbsArg   Im   Re   Conjugate   ToPolarCoordinates

Function Repository: UnwindingNumber

History

Introduced in 1988 (1.0) | Updated in 2007 (6.0) 2021 (13.0)

Wolfram Research (1988), Arg, Wolfram Language function, https://reference.wolfram.com/language/ref/Arg.html (updated 2021).

Text

Wolfram Research (1988), Arg, Wolfram Language function, https://reference.wolfram.com/language/ref/Arg.html (updated 2021).

CMS

Wolfram Language. 1988. "Arg." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2021. https://reference.wolfram.com/language/ref/Arg.html.

APA

Wolfram Language. (1988). Arg. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Arg.html

BibTeX

@misc{reference.wolfram_2025_arg, author="Wolfram Research", title="{Arg}", year="2021", howpublished="\url{https://reference.wolfram.com/language/ref/Arg.html}", note=[Accessed: 05-December-2025]}

BibLaTeX

@online{reference.wolfram_2025_arg, organization={Wolfram Research}, title={Arg}, year={2021}, url={https://reference.wolfram.com/language/ref/Arg.html}, note=[Accessed: 05-December-2025]}

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