title: Determining if two rays intersect
body: <p>I have two rays on a 2D plane that extend to infinity, but both have a starting point. They are both described by a starting point and a vector in the direction of the ray extending to infinity. I want to find out if the two rays intersect, but I don't need to know where they intersect (it's part of a collision detection algorithm).</p>
  
  <p>Everything I have looked at so far describes finding the intersection point of two lines or line segments. Is there a fast algorithm to solve this?</p>