[Inkscape-user] Round single corner in a square

Hi, I want to round a single corner of a square, but I can't obtain what I want.

Inside the square there is a circle and I'd like to have the corner with the same roundness of the circle.

What I did till now is: 1) converting the square to a path 2) creating two new nodes in the middle of each side of the corner 3) move handles of the corner to round it

This doesn't work very well, so I tried to duplicate the circle and cut the corner dividing paths. Maybe this is a better solution but I can't exactly align the cutting circle with the first one (I have to align them diagonally).

Is there an easier way to do this? Or a tutorial or something about rounding single corners?

Thank you, Carlo