# Complex.Atan Method (Complex)

.NET Framework (current version)

Returns the angle that is the arc tangent of the specified complex number.

Namespace:   System.Numerics
Assembly:  System.Numerics (in System.Numerics.dll)

## Syntax

```public static Complex Atan(
Complex value
)
```

#### Parameters

value
Type: System.Numerics.Complex

A complex number.

#### Return Value

Type: System.Numerics.Complex

The angle that is the arc tangent of value.

## Remarks

The Atan method for complex numbers corresponds to the Math.Atan method for real numbers.

The Atan method uses the following formula:

ImaginaryOne / new Complex(2.0, 0.0)) * (Log(One - ImaginaryOne * value) - Log(One + ImaginaryOne * value)

## Examples

The following example illustrates the Atan method. It shows that passing the value returned by the Atan method to the Tan method returns the original Complex value.

```using System;
using System.Numerics;

public class Example
{
public static void Main()
{
Complex[] values = { new Complex(2.5, 1.5),
new Complex(2.5, -1.5),
new Complex(-2.5, 1.5),
new Complex(-2.5, -1.5) };
foreach (Complex value in values)
Console.WriteLine("Tan(Atan({0})) = {1}",
value, Complex.Tan(Complex.Atan(value)));
}
}
// The example displays the following output:
//       Tan(Atan((2.5, 1.5))) = (2.5, 1.5)
//       Tan(Atan((2.5, -1.5))) = (2.5, -1.5)
//       Tan(Atan((-2.5, 1.5))) = (-2.5, 1.5)
//       Tan(Atan((-2.5, -1.5))) = (-2.5, -1.5)
```

## Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone
Available since 8.1