title: 2D geometry: how to check if a point is inside an angle
body: <p>i  have the following geometrical issue in 2D:</p>
  
  <p>i have a point from which i cast an infinite angle (2D-cone) which is given by a direction and an angle. (the point and the direction form a vector and to each side half of the angle forms the 2D-cone)</p>
  
  <p>now i want to check if another point in 2D is inside this cone or outside.</p>
  
  <p>how can this be achieved?
  thanks!</p>