Arcs
The CreateArcElement1 function is easiest for 2D drawings because it only requires three points: starting and ending points along the arc along with the center of the arc.
Dim ptStart As Point3d Dim ptEnd As Point3d Dim ptOrigin As Point3d Dim oArc As ArcElement
Set oArc = CreateArcElement1(Nothing, ptStart, ptOrigin, ptEnd) ActiveModelReference.AddElement oArc