# Arcversine
> Compute the [inverse versed sine][inverse-versed-sine].
The [inverse versed sine][inverse-versed-sine] is defined as
## Usage
```javascript
var aversin = require( '@stdlib/math/base/special/aversin' );
```
#### aversin( x )
Computes the [inverse versed sine][inverse-versed-sine].
```javascript
var v = aversin( 0.0 );
// returns 0.0
v = aversin( 3.141592653589793/2.0 );
// returns ~2.1783
v = aversin( 3.141592653589793/6.0 );
// returns ~1.0742
```
If `x < 0`, `x > 2`, or `x` is `NaN`, the function returns `NaN`.
```javascript
var v = aversin( -1.0 );
// returns NaN
v = aversin( 3.14 );
// returns NaN
v = aversin( NaN );
// returns NaN
```
## Examples
```javascript
var linspace = require( '@stdlib/array/linspace' );
var aversin = require( '@stdlib/math/base/special/aversin' );
var x = linspace( 0.0, 2.0, 100 );
var i;
for ( i = 0; i < x.length; i++ ) {
console.log( aversin( x[ i ] ) );
}
```
[inverse-versed-sine]: https://en.wikipedia.org/wiki/Versine
