Tangent Arc between Two Intersecting Circles

[Anonymous]

Here is where I am.

family type - conceptual mass 
revit 2013

I am trying to create an arc between two intersecting circles 
whose start and end points are at x and y dimensions on the two circles
and whose arc is defined by the tangents of the two intersecting circles

I have attached an image of the sketch.

Any suggestions?

Thanks
Erik

[constantin.stroescu]

 in Mass Editor  ...try to make two arcs that follow the two circles path (short arcs only in the area you need ..max 180 grads) 

then from Draw use the comand Fillet Arc...it wil work