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# Math.Atan2 Method

Visual Studio 2010

Returns the angle whose tangent is the quotient of two specified numbers.

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

## Syntax

```public static double Atan2(
double y,
double x
)
```

#### Parameters

y
Type: System.Double
The y coordinate of a point.
x
Type: System.Double
The x coordinate of a point.

#### Return Value

Type: System.Double
An angle, θ, measured in radians, such that -π θ π, and tan(θ) = y / x, where (x, y) is a point in the Cartesian plane. Observe the following:
• For (x, y) in quadrant 1, 0 < θ < π/2.

• For (x, y) in quadrant 2, π/2 < θ π.

• For (x, y) in quadrant 3, -π < θ < -π/2.

• For (x, y) in quadrant 4, -π/2 < θ < 0.

For points on the boundaries of the quadrants, the return value is the following:
• If y is 0 and x is not negative, θ = 0.

• If y is 0 and x is negative, θ = π.

• If y is positive and x is 0, θ = π/2.

• If y is negative and x is 0, θ = -π/2.

If x or y is NaN, or if x and y are either PositiveInfinity or NegativeInfinity, the method returns NaN.

## Remarks

The return value is the angle in the Cartesian plane formed by the x-axis, and a vector starting from the origin, (0,0), and terminating at the point, (x,y).

## Examples

The following example demonstrates how to calculate the arctangent of an angle and a vector. The resulting value is displayed in 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 result;

// Calculate the tangent of 30 degrees.
angle = 30;
Console.WriteLine("The tangent of 30 degrees is {0}.", result);

// Calculate the arctangent of the previous tangent.
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.";

Console.WriteLine(line1, Environment.NewLine);
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

#### .NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

#### .NET Framework Client Profile

Supported in: 4, 3.5 SP1

#### Portable Class Library

Supported in: Portable Class Library

## Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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