# C# | Math.Atan() Method

• Last Updated : 31 Jan, 2019

Math.Atan() is an inbuilt Math class method which returns the angle whose tangent is given as a double value argument. If the argument is NaN, then the result will be NaN.

Syntax:

```public static double Atan(double num)
```

Parameter:

num: It is the number that represents a tangent and type of this parameter is System.Double.

Return Type: Returns an angle Θ, measured in radians and its type is System.Double. Here the angle is always measured in radians, such that -π/2 ≤ Θ ≤ π/2.

Examples:

```Input  : Math.Atan(1)
Output : 0.785398163397448

Input  : Math.Atan(0.0)
Output : 0

Input  : Math.Atan(-0.0)
Output : 0

Input  : Math.Atan(Double.PositiveInfinity)
Output : 1.5707963267949

Input  : Math.Atan(Double.NegativeInfinity)
Output : -1.5707963267949
```

Program: To illustrate the Math.Atan() method

 `// C# program to demonstrate working``// of Math.Atan() method``using` `System;`` ` `class` `Geeks {`` ` `    ``// Main Method``    ``public` `static` `void` `Main(String []args)``    ``{``        ``double` `a = Math.PI;``         ` `        ``// using Math.Atan() method ``        ``Console.WriteLine(Math.Atan(a));`` ` `        ``double` `d = 0.0;``        ``double` `e = -0.0;``        ``double` `posi = Double.PositiveInfinity;``        ``double` `nega = Double.NegativeInfinity;``        ``double` `nan = Double.NaN;`` ` `        ``Console.WriteLine(Math.Atan(1));`` ` `        ``// Input positive zero``        ``// Output positive zero``        ``Console.WriteLine(Math.Atan(d));`` ` `        ``// Input negative zero``        ``// Output positive zero``        ``Console.WriteLine(Math.Atan(e));``         ` `        ``// input PositiveInfinity``        ``// Output 1.5707963267949``        ``Console.WriteLine(Math.Atan(posi));``         ` `        ``// input NegativeInfinity``        ``// Output -1.5707963267949``        ``Console.WriteLine(Math.Atan(nega));``         ` `        ``// input NaN``        ``// Output NaN``        ``Console.WriteLine(Math.Atan(nan));``    ``}``}`
Output:
```1.26262725567891
0.785398163397448
0
0
1.5707963267949
-1.5707963267949
NaN
```

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