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# asin (<valarray>)

Visual Studio 2015

Operates on the elements of an input valarray, returning a valarray whose elements are equal to the arcsine of the elements of the input valarray.

```template<class Type>
valarray<Type> asin(
const valarray<Type>& _Left
);
```

## Parameters

_Left

The input valarray whose elements are to be operated on by the member function.

## Return Value

A valarray whose elements are equal to the arcsine of the elements of the input valarray.

## Remarks

The units of the returned elements are in radians.

The return value is a principal value between +pi/2 and –pi/2 that is consistent with the sine value input.

## Example

```// valarray_asin.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>
#include <iomanip>

int main( )
{
using namespace std;
double pi = 3.14159265359;
int i;

valarray<double> va1 ( 9 );
for ( i = 0 ; i < 9 ; i++ )
va1 [ i ] =  0.25 * i - 1;
valarray<double> va2 ( 9 );

cout << "The initial valarray is:";
for (i = 0 ; i < 9 ; i++ )
cout << " " << va1 [ i ];
cout << endl;

va2 = asin ( va1 );
cout << "The arcsine of the initial valarray is:\n";
for (i = 0 ; i < 9 ; i++ )
cout << setw(10) << va2 [ i ]
<< "  radians, which is  "
<< setw(11) << (180/pi) * va2 [ i ]
<< "  degrees" << endl;
}
```
```The initial valarray is: -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
The arcsine of the initial valarray is:
-1.5708  radians, which is          -90  degrees
-0.848062  radians, which is     -48.5904  degrees
-0.523599  radians, which is          -30  degrees
-0.25268  radians, which is     -14.4775  degrees
0  radians, which is            0  degrees
0.25268  radians, which is      14.4775  degrees
0.523599  radians, which is           30  degrees
0.848062  radians, which is      48.5904  degrees
1.5708  radians, which is           90  degrees```