Export (0) Print
Expand All

Math.Atan2 Method

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

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

public static double Atan2 (
	double y,
	double x
)
public static double Atan2 (
	double y, 
	double x
)
public static function Atan2 (
	y : double, 
	x : double
) : double
Not applicable.

Parameters

y

The y coordinate of a point.

x

The x coordinate of a point.

Return Value

An angle, θ, measured in radians, such that -πθπ, 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 < θπ.

  • 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 x is 0 and y is not negative, θ = 0.

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

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

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

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).

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 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.
*/

// This example demonstrates Math.Atan()
//                           Math.Atan2()
//                           Math.Tan()

import System.*;

class Sample
{
    public static void main(String[] args)
    {
        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 = System.Math.Tan(radians);
        Console.WriteLine("The tangent of 30 degrees is {0}.", 
            System.Convert.ToString(result));

        // Calculate the arctangent of the previous tangent.
        radians = System.Math.Atan(result);
        angle = radians * (180 / Math.PI);
        Console.WriteLine("The previous tangent is equivalent to {0} degrees.",
            System.Convert.ToString(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 = System.Math.Atan2(y, x);
        angle = radians * (180 / Math.PI);

        Console.WriteLine(line1, Environment.get_NewLine());
        Console.WriteLine(line2, System.Convert.ToString(x), 
            System.Convert.ToString(y), System.Convert.ToString(radians));
        Console.WriteLine(line3, System.Convert.ToString(angle));
    } //main
} //Sample

/*
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.
*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

Community Additions

ADD
Show:
© 2014 Microsoft