I am studying pursuit curves where a fast pirate ship which pursues a heavily laden treasure ship which tracks along a straight line. The ratio of the speeds of the ships is r > 1 (which is fixed) and the pirate captain spies the treasure ship initially at a distance d km away.
There s a step within the calculations thatI am failing to understand:
I do not understand why or how the speed is equal to r(dY/dt)
Any help is greatly appreciated! thank you