Three Touching Circles on a Line

The radius

r

1

of the blue circle is 2.

The radius

r

2

of the green circle is 0.5.

The radius

r

3

of the purple circle is

r

1

r

2



r

1

+

r

2



= 0.222222.

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.

Details

Idea taken from Sangaku.

External Links

Tangent Circles (Wolfram MathWorld)

Permanent Citation

Noel Patson

"Three Touching Circles on a Line"
http://demonstrations.wolfram.com/ThreeTouchingCirclesOnALine/
Wolfram Demonstrations Project
Published: March 7, 2011