Half Circle on Slabs

How do you make half circles with slabs?  Thanks! 

Either draw a rectangle with short sides and edit a long edge to have a radius, then reduce the opposite side or draw a triangle shape and set radius on 2 edges. Or draw shapes, select - form polygon, then select convert shape to site line, or use as a guide to trace. Or draw walls and create the shape, then use auto trace for a concrete slab. Some options get a bit segmented.

Thanks Mark.  Good options.