You can create a shape with arcs like the one you created before with lines.

When you click on the shape below you will be able to edit the parameters for one of the arcs on the right. Also you can drag the currently selected arc by it's origin point. Notice how the polar coordinate grid moves with its origin. That is because the arc is drawn relative to it's own origin, not to the origin of the cartesian coordinates grid.

There are two arcs that create the shape. Each time you click on the shape, the arc that is editable will change. Try making this shape into a letter O.