# C++ <complex> - atan() Function

The C++ <complex> atan() function returns the complex arc tangent of a complex number z. It is a function on complex plane, and has two branch cuts:

• Extends from 1j along the imaginary axis to ∞j, continuous from the right.
• Extends from -1j along the imaginary axis to -∞j, continuous from the left.

Mathematically, it can be expressed as: ### Syntax

```template<class T> complex<T> atan (const complex<T>& z);
```

### Parameters

 `z` Specify the complex number.

### Return Value

Returns the complex arc tangent of z.

### Example:

The example below shows the usage of <complex> atan() function.

```#include <iostream>
#include <complex>
using namespace std;

int main (){
complex<double> z1 (2, 2);
complex<double> z2 (2, 0);
complex<double> z3 (0, 2);

//calculate the complex arc tangent
cout<<"atan(z1): "<<atan(z1)<<"\n";
cout<<"atan(z2): "<<atan(z2)<<"\n";
cout<<"atan(z3): "<<atan(z3)<<"\n";

return 0;
}
```

The output of the above code will be:

```atan(z1): (1.31122,0.238878)
atan(z2): (1.10715,0)
atan(z3): (1.5708,0.549306)
```

❮ C++ <complex> Library

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