From FreeCAD Documentation
- There are several ways to invoke the tool:
- The cursor changes to a cross with the tool icon.
- Pick the center of the arc.
- Pick an endpoint of one of the axes of the arc, this also defines one of its radii.
- Pick the start point of the arc, this also defines the other radius of the arc.
- Pick the endpoint of the arc.
- The arc of ellipse is created, including a set of internal geometry (major axis, minor axis and two foci).
- If the tool runs in continue mode:
- Optionally keep creating arcs.
- To finish, right-click or press Esc, or start another geometry or constraint creation tool.