Use the gui techniques shown fig

.

Answer

<script>

function calculate() {

var circumference = 2 * Math.PI * radius;

var area = Math.PI * Math.pow(radius, 2);

}

</script>

<input type="number" id="radius" step="0.01">

<button onclick="calculate()">Calculate</button>

<th>Value</th>

</tr>

<tr>

<td>Circumference</td>

<td id="area"></td>

</tr>