ROUND allows you to create an arc that is tangent to
the endpoint of an existing curve (excluding circles).

Select a tangent entity near the desired endpoint.
The endpoint that is closest to the selection point is
marked with an X, and it is projected to the current
construction plane. This point is used as the starting
position for the arc.

Indicate an endpoint for the arc, using an option from the
Position Menu. The endpoint is projected to the current
construction plane.

Assign a direction for the arc: CLKWSE (clockwise) or
CCLKWSE (counter-clockwise). The arc is created in the
current construction plane.
