How to write a point on an ellipse using r and theta We can write any point on the circle as $(r\cos\theta,r\sin\theta$), Can we do samething for the ellipse? 


With $a$ the major and $b$ the minor semiaxis, you get $(a\cos\theta,b\sin\theta)$ for your orientation. A rotated ellipse will be a bit harder, for this I'd compute the point in its unoriented form and then rotate afterwards. Note that the angle $\theta$ in the above is a parameter, but is not actually the angle as it is in the circular case.
