Two small spheres of mass m are suspended from strings of length that are connected at a

Question:

Two small spheres of mass m are suspended from strings of length ℓ that are connected at a common point. One sphere has charge Q; the other has charge 2Q. The strings make angles θ1 and θ2 with the vertical.
(a) How are θ1 and θ2 related?
(b) Assume θ1 and θ2 are small. Show that the distance r between the spheres is given by