title: Point and ellipse (rotated) position test: algorithm
body: <p>How to test if a point P = [xp,yp] is inside/outside some rotated ellipse given by the centre C=[x,y], a, b, and phi ( angle of rotation)?</p>
  
  <p>At this moment I am using the following solution: rotate ellipse and point by the angle -phi and then the common test for a position of the point and "non rotated" ellipse. </p>
  
  <p>But there are a lot of tested points (thousands) and I find this solution as slow. Is there any direct and more efficient way to get a position of the rotated ellipse and point?</p>
  
  <p>I do not need a code but the algorithm. Thanks for your help.</p>