C# | Math.Atan2() Method

Math.Atan2() is an inbuilt Math class method which returns the angle whose tangent is the quotient of two specified numbers. Basically, it returns an angle θ (measured in radian) whose value lies between -π and π. This is a counterclockwise angle lies between the positive x-axis, and the point (x, y).

Syntax:

public static double Atan2(double value1, double value2)

Parameters:

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

Return Type: Returns the angle Θ of type System.Double.

Note: An angle, θ(measured in radians), such that -π ≤ θ ≤ π, and tan(θ) = value1 / value2, where (value1, value2) are the points in the cartesian plane. There are two conditions for the return values:

• When the points lies in the Cartesian plane
• When the points lies on the boundaries of the quadrants

Below are the programs to demonstrate the Math.Atan2() Method when the points lies in the Cartesian plane:

• Program 1: If point(value1, value2) lies in the first quadrant i.e., 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));     } }

  Output:

  45
  

• Program 2: If point(value1, value2) lies in the second quadrant i.e., 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));     } }

  Output:

  135
  

• Program 3: If point(value1, value2) lies in the third quadrant i.e., -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));     } }

  Output:

  -135
  

• Program 4: If point(value1, value2) lies in the fourth quadrant i.e., -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));     } }

  Output:

  -45
  

Below are the programs to demonstrate the Math.Atan2() Method when the points lies on the boundaries of the quadrants:

• Program 1: If value1 is 0 and value2 is not negative i.e. 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));     } }

  Output:

  0
  

• Program 2: If value1 is 0 and value2 is negative i.e. 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));     } }

  Output:

  180
  

• Program 3: If value1 is positive and value2 is 0 i.e. 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));     } }

  Output:

  90
  

• Program 4: If value1 is negative and value2 is 0 i.e. 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));     } }

  Output:

  -90
  

• Program 5: If value1 is 0 and value2 is 0 i.e. 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));     } }

  Output:

  0
  

Important Point to Remember: If value1 or value2 is NaN, or if value1 and value1 are either PositiveInfinity or NegativeInfinity, the method returns NaN.

Example:

NaN
NaN
NaN
NaN

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