<!DOCTYPE html>
<html>
<body>

<p>Click the button to display the arcsine of 0.5</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    document.getElementById("demo").innerHTML = Math.asin(0.5);
}
</script>

</body>
</html>