# Math.Atan2(Double, Double) 方法

## 定义

``````public:
static double Atan2(double y, double x);``````
``public static double Atan2 (double y, double x);``
``static member Atan2 : double * double -> double``
``Public Shared Function Atan2 (y As Double, x As Double) As Double``

y
Double

x
Double

#### 返回

Double

- 由于 (`x`, `y`) 在第 2 象限，因此 π/2 < θ ≤ π。- For (`x`, `y`) in quadrant 2, π/2 < θ ≤ π.

- 由于 (`x`, `y`) 在第 3 象限，因此 -π < θ < -π/2。- For (`x`, `y`) in quadrant 3, -π < θ < -π/2.

- 由于 (`x`, `y`) 在第 4 象限，因此 -π/2 < θ < 0。- For (`x`, `y`) in quadrant 4, -π/2 < θ < 0.

- 如果 y 为 0 并且 x 为负值，则 θ = π。- If y is 0 and x is negative, θ = π.

- 如果 y 为正值并且 x 为 0，则 θ = π/2。- If y is positive and x is 0, θ = π/2.

- 如果 y 为负值并且 x 为 0，则 θ = -π/2。- If y is negative and x is 0, θ = -π/2.

- 如果 y 为 0 并且 x 为 0，则 θ = 0。- If y is 0 and x is 0, θ = 0.

## 示例

``````// This example demonstrates Math.Atan()
//                           Math.Atan2()
//                           Math.Tan()
using namespace System;
int main()
{
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);
Console::WriteLine( "The tangent of 30 degrees is {0}.", result );

// Calculate the arctangent of the previous tangent.
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()
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.
*/
``````
``````' This example demonstrates Math.Atan()
'                           Math.Atan2()
'                           Math.Tan()
Class Sample
Public Shared Sub Main()
Dim x As Double = 1.0
Dim y As Double = 2.0
Dim angle As Double
Dim result As Double

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

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

' 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."

angle = radians *(180 / Math.PI)

Console.WriteLine(line1, Environment.NewLine)
Console.WriteLine(line3, angle)
End Sub
End Class
'
'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.
'
``````