<canvas id="cas" width="300" height="300"></canvas>
<script>
    var ct = document.getElementById('cas').getContext('2d');
    ct.beginPath();
    ct.strokeStyle = 'green';
    ct.lineWidth = 5;
    ct.arc(100, 120, 25, Math.PI / 6, 5 * Math.PI / 6, false);
    ct.stroke();
</script>