Potential due to a system at polar coordinates $\;(r , \theta)\;$ is given by $\;\large\frac{\alpha \;cos \theta}{r^2}\;$ Find the magnitude of electric field at that point if $\;\alpha=3 Vm^2\;,(r , \theta)=(\sqrt{3} ,tan^{-1} \large\frac{1}{\sqrt{2}}). $

Question

$(a)\;\sqrt{3} \;Vm^{-1}\qquad(b)\;3\;Vm^{-1}\qquad(c)\;3 \sqrt{3} \;Vm^{-1}\qquad(d)\;1 \;Vm^{-1}$