it can catch??? r u sure? i just laid out a sketch of a proof that it does not. i can prolly explain it in words better.... say you aim a bullet at a bird. as soon as the bird hears the gun shot, it flies away...the bullet takes some time to travel to the bird, so during this time, the bird will have travelled away from its initial location, and so does not get killed. (this is an extreme example, because in reality, the bird's response time is less than the time for the bullet to get to it, which is why it gets killed). the exact same thinking can be applied to your example to show why A will never catch B... but anyway, dont know if you had a chance to check out the readily-available solution to your problem set at: - http://mathworld.wolfram.com/PursuitCurve.html anyway, good luck.