Operations:
Step 1: click the “Draw” button and select the “Arc” command.
Step 2: specify the arc start point by dragging or clicking on the drawing area.
Step 3: adjust the arc start point or specify the endpoint of the arc by clicking the second point on the drawing area.
Step 4: adjust the endpoint or specify one point on arc.
Step 5: adjust current point or tap “✓” to confirm it.