The earth moves in a circular orbit with radius R around the sun with speed V. A comet also orbits the sun in a path such that the perihelion is at \frac{R}{2} at a speed 2V. The question is to deduce from the conversation of angular momentum that the angle at which their orbits cross is \frac{\pi}{4}.

Now, I know that angular momentum is r^{2}\dot{\theta}m but I am unsure how to apply this to the question and I am unsure what \dot{\theta} is representing here. And do I also have to consider the momentum of the earth?