1. The problem statement, all variables and given/known data Charges +/- q separated by a distance d make a dipole with dipole moment qd. For large r the potential approaches qdcosθ/(4πε0r²). For θ=0, how large must r be so that the asymptotic function is accurate to 1%? 2. Relevant equations Exact V= q1/(4πε0r) + q2 /(4πε0r) Approximate V= qdcosθ/(4πε0r²) 3. The attempt at a solution I understand that the following statement must be true: Vexact - Vapproximate ≤ 1.0%(Vexact) q1/(4πε0r) + q2 /(4πε0(r-d)) - qdcosθ/(4πε0r²) ≤ 1.0 %. If we cancel all like constants; 1/r - 1/(r-d) - d/r²) ≤ 1.0 % I do not understand where to go from here, or even if my approach towards this is correct. Thank you in advance to all those who are reading.