# 1.3 arc

    arc [ item <id> ] [at] <vector> radius <length>
        from <angle> to <angle> [ with { <option> } ]

Arcs (curves with constant radius of curvature, that is, segments of circles) may be drawn on multiplot canvases using the `arc` command. The `at` modifier specifies the coordinates of the center of curvature, from which all points on the arc are at the distance given following the `radius` modifier. The angles `start` and `finish`, measured clockwise from the vertical, control where the arc begins and ends. For example, the command

    arc at 0,0 radius 2 from 90 to 270

would draw a semi-circle beneath the line , centered on the origin with radius . The usual style modifiers for lines may be passed after the keyword `with`; if the `fillcolor` modifier is specified then the arc will be filled to form a pie-chart slice.

All vector graphics objects placed on multiplot canvases receive unique identification numbers which count sequentially from one, and which may be listed using the `list` command. By reference to these numbers, they can be deleted and subsequently restored with the `delete` and `undelete` commands respectively.