Atan Method

# Math.Atan Method (Double)

.NET Framework 4.6 and 4.5

Returns the angle whose tangent is the specified number.

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

## Syntax

```public static double Atan(
double d
)
```

#### Parameters

d
Type: System.Double

A number representing a tangent.

#### Return Value

Type: System.Double

An angle, θ, measured in radians, such that -π/2 θπ/2.

-or-

NaN if d equals NaN, -π/2 rounded to double precision (-1.5707963267949) if d equals NegativeInfinity, or π/2 rounded to double precision (1.5707963267949) if d equals PositiveInfinity.

## Remarks

A positive return value represents a counterclockwise angle from the x-axis; a negative return value represents a clockwise angle.

Multiply the return value by 180/Math.PI to convert from radians to degrees.

## Examples

The following example demonstrates how to calculate the arctangent of a value and display it to the console.

```// This example demonstrates Math.Atan()
//                           Math.Atan2()
//                           Math.Tan()
using System;

class Sample
{
public static void Main()
{
double x = 1.0;
double y = 2.0;
double angle;
double radians;
double result;

// Calculate the tangent of 30 degrees.
angle = 30;
radians = angle * (Math.PI/180);
result = Math.Tan(radians);
Console.WriteLine("The tangent of 30 degrees is {0}.", result);

// Calculate the arctangent of the previous tangent.
radians = Math.Atan(result);
angle = radians * (180/Math.PI);
Console.WriteLine("The previous tangent is equivalent to {0} degrees.", angle);

// Calculate the arctangent of an angle.
String line1 = "{0}The arctangent of the angle formed by the x-axis and ";
String line2 = "a vector to point ({0},{1}) is {2}, ";
String line3 = "which is equivalent to {0} degrees.";

radians = Math.Atan2(y, x);
angle = radians * (180/Math.PI);

Console.WriteLine(line1, Environment.NewLine);
Console.WriteLine(line2, x, y, radians);
Console.WriteLine(line3, angle);
}
}
/*
This example produces the following results:

The tangent of 30 degrees is 0.577350269189626.
The previous tangent is equivalent to 30 degrees.

The arctangent of the angle formed by the x-axis and
a vector to point (1,2) is 1.10714871779409,
which is equivalent to 63.434948822922 degrees.
*/
```

## Version Information

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

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