# C# | Math.Atan() Method

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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