Hello all. I am trying to change: E = (1/r) ar To rectangular coordinate system. Where ar is a unit vector. So I know r = √(x^2 + y^2) i also think ar = ax+ay, where ax and ay are unit vectors along the x axis and y axis respectively. So that would give me: E = (1/√(x^2 + y^2)) (ax + ay) = ax/√(x^2 + y^2) + ay/√(x^2 + y^2)... Which is wrong. The correct answer is: (x ax)/(x^2 + y^2) + (y ay)/(x^2 + y^2) So what am I doing wrong? Thank you.