C# Math.Atan2()用法及代碼示例

Math.Atan2()是內置的Math類方法，該方法返回其切線為兩個指定數字的商的角度。本質上，它返回一個角度θ(以弧度為單位)，該角度的值介於-π和π之間。這是正x軸和點(x，y)之間的逆時針角度。

用法:

public static double Atan2(double value1, double value2)

參數：

• value1:類型System.Double的點的y坐標。
  value2:類型點的x坐標係統雙。

返回類型：返回System.Double類型的角度Θ。

注意：角度θ(以弧度為單位)，使-π≤θ≤π，且tan(θ)= value1 /value2，其中(value1，value2)是笛卡爾平麵中的點。返回值有兩個條件：

• 當點位於笛卡爾平麵中時
• 當點位於象限的邊界上時

以下是演示當點位於笛卡爾平麵中時的Math.Atan2()方法的程序：

• 示例1:如果point(value1，value2)位於第一象限，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)); 
      } 
  }

  輸出：

  45
  

• 示例2:如果point(value1，value2)位於第二象限即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)); 
      } 
  }

  輸出：

  135
  

• 示例3:如果point(value1，value2)位於第三象限，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)); 
      } 
  }

  輸出：

  -135
  

• 示例4:如果point(value1，value2)位於第四個象限，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)); 
      } 
  }

  輸出：

  -45
  

以下是演示當點位於象限邊界上時的Math.Atan2()方法的程序：

• 示例1:如果value1為0且value2不為負，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)); 
      } 
  }

  輸出：
  

  0
  

• 示例2:如果value1為0且value2為負，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)); 
      } 
  }

  輸出：

  180
  

• 示例3:如果value1為正且value2為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)); 
      } 
  }

  輸出：

  90
  

• 示例4:如果value1為負且value2為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)); 
      } 
  }

  輸出：

  -90
  

• 示例5:如果value1為0且value2為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)); 
      } 
  }

  輸出：

  0
  

要記住的重要點：如果value1或value2為NaN，或者value1和value1為PositiveInfinity或NegativeInfinity，則該方法返回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

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