To get the tangent of a number in JavaScript, use the Math.tan() method. This method returns the tangent of a number. The tan method returns a numeric value that represents the tangent of the angle.
Example
You can try to run the following code to get the tangent of a number −
<html>
<head>
<title>JavaScript Math tan() Method</title>
</head>
<body>
<script>
var value = Math.tan( -30 );
document.write("First Value : " + value );
var value = Math.tan( 90 );
document.write("<br />Second Value : " + value );
var value = Math.tan( 45 );
document.write("<br />Third Value : " + value );
var value = Math.tan( Math.PI/180 );
document.write("<br />Fourth Value : " + value );
</script>
</body>
</html>