​x
 
<!DOCTYPE html>
<html>
​
<body>
    <p id="mathGen"></p>
    <input type="text" id="num" />
    <button onclick="getSqrt()">Square Root number</button>
<script>
    function getSqrt(){
        var x = document.getElementById("num").value; 
        document.getElementById("mathGen").innerHTML = Math.sqrt(x);
    }   
</script>
</body>
​
</html>