Click this icon to insert an arc tangent to two entities. Where more than one tangent exists, the point of entity selection determines the tangents used to define the arc. This is one of the more difficult arc tools to understand and use. It requires you to have two arcs, chamfers, circles or lines already drawn to refer to.
1. Turn off your constraints.
2. Click on the first entity you wish the arc to be tangent to.
3. Click on the second entity you wish the arc to be tangent to. The arc is now constrained to be tangent to the selected entities.
4. The starting angle will be at the intersection of the circle and the line. Select the first location and click the left mouse button. This location specifies the starting angle of the arc.
5. The ending angle is at the intersection of the arc and this line. Specify the ending angle and create the arc by selecting the second location.