# Three touching circles on a line

The radius of the middle circle (purple) of three circles all touching each other and a line is given by a formula in terms of the radii of the two outside circles. Drag the points to vary the outside circles.

The radius of the middle circle (purple) of three circles all touching each other and a line is given by a formula in terms of the radii of the two outside circles. Drag the points to vary the outside circles.