A pair of coalescing soap bubbles, with rA = 200. You can adjust rB to see the effect on the intermediate surface, which is an auxiliary circle with radius rC.

rB = 100

Their internal pressures reach an equilibrium when 1 / rA = 1 / rC - 1 / rB, and the tangents of the three arcs meet at 120º at the points of intersection.

Inspired by Two Coalescing Soap Bubbles.

See also