As the coordinates of two tangent points are fixed by some constraints. I would like to fit a circular curves to joint them together. If begin radius say is 80m. How can I find the second radius which shown in attached file ?
Doing it graphically in CAD is easier using the AutoCAD 'ARC' command with 'Continue' arc.
Knowing the end point of first arc (R1 = 80000), and knowing the PT (tangent point of the end of the second arc) 'ARC Continue' will continue a tangent arc from the PCC (compound curve point) to the PT, then use 'dimension' to obtain the drawn radius.