Three charges are arranged on vertices of eq. triangle of side d.

point A(-q),point B(2q),point c(-q).Find dipole moment of the combination.

                    A- q                                 separate 2q in q and q 

        q

    B    q                      C -q

from A to B DIPOLE MOMENT = qd

from C to B DIPOLE MOMENT = qd

net dipole moment is the vector sum of the above two

i.e   qd cos30 + qd cos30 = (root3)qd