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

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

• Extends right from 1 along the real axis to ∞, continuous from below.
• Extends left from -1 along the real axis to -∞, continuous from above.

Mathematically, it can be expressed as: For any z, asin(z) = acos(-z) - 𝜋/2

### Syntax

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

### Parameters

 `z` Specify the complex number.

### Return Value

Returns the complex arc sine of z.

### Example:

The example below shows the usage of <complex> asin() 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 sine
cout<<"asin(z1): "<<asin(z1)<<"\n";
cout<<"asin(z2): "<<asin(z2)<<"\n";
cout<<"asin(z3): "<<asin(z3)<<"\n";

return 0;
}
```

The output of the above code will be:

```asin(z1): (0.754249,1.73432)
asin(z2): (1.5708,1.31696)
asin(z3): (0,1.44364)
```

❮ C++ <complex> Library

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