C＃| Math.Atan2()方法

Math.Atan2()是一个内置的Math类方法，该方法返回其切线为两个指定数字的商的角度。基本上，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。

句法：

public static double Atan2(double value1, double value2)

参数：

value1: y coordinate of the point of type System.Double.
value2: x coordinate of the point of type System.Double.

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)，使得-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
• 当这些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：

• 程序1：如果point(value1，value2)位于第一象限，即0 <θ<π/ 2

  // 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
  

• 程序2：如果point(value1，value2)位于第二象限，即π/ 2 <θ≤π

  // 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
  

• 程序3：如果point(value1，value2)位于第三象限，即-π<θ<-π/ 2

  // 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
  

• 程序4：如果point(value1，value2)位于第四象限，即-π/ 2 <θ<0

  // 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：

• 程序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
  

• 程序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
  

• 程序3：如果value1为正，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
  

• 程序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
  

• 程序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
  

要记住的要点：如果value1或value2是NaN ，或者value1和value1是PositiveInfinity或NegativeInfinity ，则该方法将返回NaN 。

例子：

// 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));
          
         
    }
}

输出：

NaN
NaN
NaN
NaN

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