C# Math.Atan2()用法及代码示例

Math.Atan2()是内置的Math类方法，该方法返回其切线为两个指定数字的商的角度。本质上，它返回一个角度θ(以弧度为单位)，该角度的值介于-π和π之间。这是正x轴和点(x，y)之间的逆时针角度。

用法:

public static double Atan2(double value1, double value2)

参数：

• value1:类型System.Double的点的y坐标。
  value2:类型点的x坐标系统双。

返回类型：返回System.Double类型的角度Θ。

注意：角度θ(以弧度为单位)，使-π≤θ≤π，且tan(θ)= value1 /value2，其中(value1，value2)是笛卡尔平面中的点。返回值有两个条件：

• 当点位于笛卡尔平面中时
• 当点位于象限的边界上时

以下是演示当点位于笛卡尔平面中时的Math.Atan2()方法的程序：

• 示例1:如果point(value1，value2)位于第一象限，即0

  // C# program to demonstrate the 
  // Math.Atan2() Method when point 
  // lies in first quadrant 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(10, 10) * (180 / Math.PI)); 
      } 
  }

  输出：

  45
  

• 示例2:如果point(value1，value2)位于第二象限即π/2

  // C# program to demonstrate the 
  // Math.Atan2() Method when point 
  // lies in second quadrant 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(10, -10) * (180 / Math.PI)); 
      } 
  }

  输出：

  135
  

• 示例3:如果point(value1，value2)位于第三象限，即-π

  // C# program to demonstrate the 
  // Math.Atan2() Method when point 
  // lies in third quadrant 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(-10, -10) * (180 / Math.PI)); 
      } 
  }

  输出：

  -135
  

• 示例4:如果point(value1，value2)位于第四个象限，即-π/2

  // C# program to demonstrate the 
  // Math.Atan2() Method when point 
  // lies in fourth quadrant 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(-10, 10) * (180 / Math.PI)); 
      } 
  }

  输出：

  -45
  

以下是演示当点位于象限边界上时的Math.Atan2()方法的程序：

• 示例1:如果value1为0且value2不为负，即θ= 0

  // C# program to demonstrate the 
  // Math.Atan2() Method when value1  
  // is 0 and value2 is not negative 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(0, 10) * (180 / Math.PI)); 
      } 
  }

  输出：
  

  0
  

• 示例2:如果value1为0且value2为负，即θ=π

  // C# program to demonstrate the 
  // Math.Atan2() Method when value1  
  // is 0 and value2 is negative 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(0, -10) * (180 / Math.PI)); 
      } 
  }

  输出：

  180
  

• 示例3:如果value1为正且value2为0，即θ=π/2

  // C# program to demonstrate the 
  // Math.Atan2() Method value1 is 
  // positive and value2 is 0 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(10, 0) * (180 / Math.PI)); 
      } 
  }

  输出：

  90
  

• 示例4:如果value1为负且value2为0，即θ=-π/2

  // C# program to demonstrate the 
  // Math.Atan2() Method value1 is 
  // negative and value2 is 0 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(-10, 0) * (180 / Math.PI)); 
      } 
  }

  输出：

  -90
  

• 示例5:如果value1为0且value2为0，即θ= 0

  // C# program to demonstrate the 
  // Math.Atan2() Method value1 is 
  // 0 and value2 is 0 
  using System; 
    
  class Geeks { 
       
      // Main method 
      public static void Main() 
      { 
          // using Math.Atan2() Method & 
          // converting result into degree 
          Console.Write(Math.Atan2(0, 0) * (180 / Math.PI)); 
      } 
  }

  输出：

  0
  

要记住的重要点：如果value1或value2为NaN，或者value1和value1为PositiveInfinity或NegativeInfinity，则该方法返回NaN。

例：

// C# program to demonstrate the Math.Atan2()  
// method when arguments are of type either  
// NaN, PositiveInfinity or NegativeInfinity  
using System; 
  
class Geeks { 
      
    // Main method 
    public static void Main() 
    { 
        double val1 = 0; 
        double val2 = Double.NaN; 
        Console.WriteLine(Math.Atan2(val1, val2)); 
          
        double val3 = Double.NaN; 
        double val4 = Double.NaN; 
        Console.WriteLine(Math.Atan2(val3, val4)); 
          
        double val5 = Double.NaN; 
        double val6 = Double.PositiveInfinity; 
        Console.WriteLine(Math.Atan2(val5, val6)); 
          
        double val7 = Double.PositiveInfinity; 
        double val8 = Double.NegativeInfinity; 
        Console.WriteLine(Math.Atan2(val7, val8)); 
          
         
    } 
}

NaN
NaN
NaN
NaN

参考：https://msdn.microsoft.com/en-us/library/system.math.atan2