Three charges `+q,+q,and-2q` are placed at the vertices of an equilateral triangle. What is the dipole moment of the system?

Explanation

Charge `-q` at C and `+q` at A from one dipole, and the remaining charge `-q` at C and `+q` at B form another dipole.

Dipole moment along CA is qa, and dipole moment along CB is also qa.
The total dipole moment (along CD) is
`P=sqrt((qa)^(2)+(qa)^(2)+2(qa)(qa)cos60^(@))=sqrt(3)qa`
P acts along CD, which bisects the angle `(60^(@))` at C.