Math.Atan2 Method
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Returns the angle whose tangent is the quotient of two specified numbers.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<SecuritySafeCriticalAttribute> _
Public Shared Function Atan2 ( _
y As Double, _
x As Double _
) As Double
[SecuritySafeCriticalAttribute]
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()
Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim x As Double = 1.0
Dim y As Double = 2.0
Dim angle As Double
Dim radians As Double
Dim result As Double
' Calculate the tangent of 30 degrees.
angle = 30
radians = angle * (Math.PI / 180)
result = Math.Tan(radians)
outputBlock.Text &= String.Format("The tangent of 30 degrees is {0}.", result) & vbCrLf
' Calculate the arctangent of the previous tangent.
radians = Math.Atan(result)
angle = radians * (180 / Math.PI)
outputBlock.Text &= String.Format("The previous tangent is equivalent to {0} degrees.", angle) & vbCrLf
' Calculate the arctangent of an angle.
Dim line1 As [String] = "{0}The arctangent of the angle formed by the x-axis and "
Dim line2 As [String] = "a vector to point ({0},{1}) is {2}, "
Dim line3 As [String] = "which is equivalent to {0} degrees."
radians = Math.Atan2(y, x)
angle = radians * (180 / Math.PI)
outputBlock.Text &= String.Format(line1, vbCrLf) & vbCrLf
outputBlock.Text &= String.Format(line2, x, y, radians) & vbCrLf
outputBlock.Text &= String.Format(line3, angle) & vbCrLf
End Sub 'Main
End Class '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.
'
// 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 radians;
double result;
// Calculate the tangent of 30 degrees.
angle = 30;
radians = angle * (Math.PI / 180);
result = Math.Tan(radians);
outputBlock.Text += String.Format("The tangent of 30 degrees is {0}.", result) + "\n";
// Calculate the arctangent of the previous tangent.
radians = Math.Atan(result);
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.