​x
 
<!DOCTYPE html>
<html>
​
<body>
    <p id="mathGen"></p>
    <input type="text" id="num1" />
    <input type="text" id="num2" />
    <button onclick="getTan2()">Tangent number</button>
<script>
    function getTan2(){
        var x = document.getElementById("num1").value; 
        var y = document.getElementById("num2").value; 
    document.getElementById("mathGen").innerHTML = Math.atan2(y,x);
    }   
</script>
</body>
​
</html>