title: python rotating a point counterclockwise by an angle
body: <p>I have this method that rotates a point counter clockwise.</p>
  
  <pre><code>def rotate(self, rad):
      self.x = math.cos(rad)*self.x - math.sin(rad)*self.y
      self.y = math.sin(rad)*self.x + math.cos(rad)*self.y
  </code></pre>
  
  <p>but when i pass it a point to rotate, only the x coordinate is rotated correctly. For example I tried to rotate the point (0,25) by π/3 . I should be getting (-22,13) since i am rounding the answers. Instead I am getting (-22,-6).</p>