Two equal opposite charges are separated from each other

Question

1) Two equal opposite charges are separated from each other with distance d create an electric dipole moment

a. Find the electric potential at point A at distance r from the midpoint of two charges (see Fig 1).

b. Suppose d << r find an approximate expression for the electric potential at point A.

Hint: user_+=√(r²+(d/2)²-2r d/2 cos?θ ), r_-=√(r²+(d/2)²-2r d/2 cos?(π-θ) ) and (1±x)^α≅1±αxfor x«1, where r_+ and r_- are distances between the positive and the negative charges to point A.

c. The magnitude of the electric dipole is p=qd. Write you answer from part b in terms of The magnitude of electric dipole p.

               Fig 1