Definition: The asin () function is used in PHP to find the arcsine of a number. In asin (x) the value of x should be between -1 and 1. The asin() function returns the arcsine of a number as a numeric value value between -PI/2 and PI/2 radians.
Also Known As: Arcsine
Examples:
<?php
echo(asin(-0.5) . "<br />");
echo(asin(-1) . "<br />");
echo(asin(0) . "<br />");
echo(asin(1) . "<br />");
echo(asin(2))
?>
This will give you the results:
-0.5235987755983
-1.5707963267949
0
1.5707963267949
NAN
