Choose RadTanTan.
Radius of circle <value>: Enter the radius or specify a point. (If you specify a point for the radius, you are prompted to specify a second point.)
Select first tangent point: Select the first entity that you want the circle to touch.
Select second tangent point: Select the second entity that you want the circle to touch.
If a circle cannot be drawn with the radius and tangent points you selected, a message is displayed in the command bar stating that no circle is possible. If two different circles are possible (based on the specifications you selected), a circle is drawn using the tangent points closest to points where you selected the entities.