Sketch half of an ellipse. 
- Select a tool that allows for an ellipse. For example, click Annotate tab Detail panel Detail panel  (Detail Line). (Detail Line).
 
-  Click Place Lines tab (or respective Place <Element> tab or Create <Element> tab) Draw panel Draw panel  (Partial Ellipse) or (Partial Ellipse) or (Pick Lines). (Pick Lines).Note: If you select Pick Lines, you can pick the edge or face of another ellipse.  
- If you selected Pick Lines, on the Options Bar optionally specify a value for Offset. Note: Offset for an ellipse is only available when you select the Pick Lines option.  
- Click in the drawing area. Snapping is enabled for the partial ellipse, and a preview ellipse displays.  
- Move the cursor away from the first point to define the direction and extent of the major axis. 
 
- Either click when the desired value displays, or type a value and press Enter. 
- Move the cursor to get the desired partial ellipse shape and either click, or type a value and press Enter.