To get the arcsine of a number in radians, use the asin() method. This method returns the arcsine in radians of a number. The asin method returns a numeric value between -pi/2 and pi/2 radians for x between -1 and 1. If the value of a number is outside this range, it returns NaN.
Example
You can try to run the following code to get the arcsine of a number −
<html>
<head>
<title>JavaScript Math asin() Method</title>
</head>
<body>
<script>
var value = Math.asin(-1);
document.write("First Value: " + value );
value = Math.asin(null);
document.write("<br />Second Value: " + value );
value = Math.asin(30);
document.write("<br />Third Value: " + value );
value = Math.asin("Demo Text");
document.write("<br />Fourth Value: " + value );
</script>
</body>
</html>