Use this feature to create an arc with a specified radius and tangent to two selected entities.
In 3D construction mode, a plane will be created from the selected entities. If both selected entities are lines, polylines, or vectors, then the plane will always be created. This plane will be at the depth of the first entity selected if the entities are at different depths with respect to this plane.
If a plane cannot be created, or if you are working in 2D construction mode, the arc will be created using the active CPlane.
Using the Function:
Select Two Tangents from the Create>Arc submenu.
Enter a start angle.
Enter an end angle.
Enter a radius value.
Select the first and second tangent entities near their points of tangency. The entities must be coplanar. The entities cannot be parallel lines.