How do I find this distance in circles?

Question

I'm trying to find the distance between the two black points in this diagram.

I know the radii, $R$ and $r$, of the circles, and I know the coordinates of the circles' centres.

Is the distance: $R +r-d$ where $d=$ the Pythagoras distance between the circles' centres?

(The black circles lie along the line between the two circles' centres, and on their perimeters)

Answer 1

If we'll write $R+r$ then we'll obtain $d$ plus distance between two black points.