drawing arc tangent to 2 curves through a specific tangent point

 From:  pressure (PEER)
11616.12 
Brian and Michael,

We're all typing at the same time :) Thank you both for working on this. Brian yours is beautiful. I think I see why Michael's works: it's avoiding having a discontinuity where the solution suddenly vanishes.

By the way, happy new year to both of you!

- Peer