Menu: Draw / Circle / Tangent to 3 Arcs 
Creates a circle tangent to three arcs or circles. You can specify whether the existing arcs will be inside or outside the new circle.
- Select the first tangent object. Click slightly outside the object to keep it outside the new circle. Click inside if you want the tangent object to be inside the new circle.
If the object is clicked slightly outside, an outward-pointing arrow appears. 
- Select the second tangent object.
If the object is clicked slightly inside, an inward-pointing arrow appears. 
- Select the third object. The tangent circle is created.
