CTR+RAD allows you to create an arc by specifying start 
and end angles, a center position, and a radius.

Enter a value for the radius and press <Enter>, or accept
the default value displayed in parentheses by pressing
<Enter>.

Enter a positive or negative start angle (in degrees) for
the arc and press <Enter>, or accept the default value in
parentheses by pressing <Enter>.

Enter an end angle in the same manner as the start angle.
Remember that the arc is always created counter-clockwise
from the start to the end angle.

Indicate the center point of the arc, using a Position 
Menu option.

In 2-D construction mode, the center point is projected to
the current construction plane, and the arc is created in
the current construction plane.

In 3-D construction mode, the arc is created in the plane
that is parallel to the current construction plane and
passes through the center point.

