# Math.Atan Method

Silverlight

Returns the angle whose tangent is the specified number.

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

## Syntax

```[SecuritySafeCriticalAttribute]
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 θ π/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 Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
double x = 1.0;
double y = 2.0;
double angle;
double result;

// Calculate the tangent of 30 degrees.
angle = 30;
radians = angle * (Math.PI / 180);
outputBlock.Text += String.Format("The tangent of 30 degrees is {0}.", result) + "\n";

// Calculate the arctangent of the previous tangent.
angle = radians * (180 / Math.PI);
outputBlock.Text += String.Format("The previous tangent is equivalent to {0} degrees.", angle) + "\n";

// 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);

outputBlock.Text += String.Format(line1, "\n") + "\n";
outputBlock.Text += String.Format(line2, x, y, radians) + "\n";
outputBlock.Text += String.Format(line3, angle) + "\n";
}
}
/*
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

#### Silverlight

Supported in: 5, 4, 3

#### Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

#### XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

## Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.