Recall that e_r points outward from the observer O and the point P. The e_theta unit vector is perpendicular to e_r and points in the positive theta direction. These two unit vectors are shown in ...

This circle has the centre at the origin and a radius of 1 unit. The point P can move around the circumference of the circle. At point P the \(x\)-coordinate is \(\cos{\theta}\) and the \(y ...