(a) What speeds do people at each location see the other traveling?
In part a, I am assuming I should be using the Lorentz velocity transformation, but am unsure of how to do this since I don't know what direction (x, y) the rockets are traveling.
In part b, if I use the relativistic Doppler Effect, I have two unknowns:
f_O = (?1- v/c / ?1 + v/c) f_S
I need to find both the velocity (v) and the observed frequency (f_O). How do I do this?
You are right to use the Lorentz transformation.
As to the axes note the text "... Klingon fighter ship approaches from the opposite direction ...".
This means the two ships move along the same straight line towards each other.
Therefore you can just choose this line ...
Velocity transformation and relativistic doppler effect is investigated.