I have a table of values for a projectile moving away from a radar station. My first column is the time (t) of 0 to 60 with time steps of 4. I then have a distance(km) of the projectile from the radar station followed by the angle(radians) of the projectile to the radar station.

The distance obviously increases by time along with a lowering of the angle of the projectile to the radar station.

I need to write a program which will work out the magnitude of velocity and acceleration for each time step (each 4 seconds upto 60) as the projectile moves away. I am confused how to do this because I am unsure how to approximate the derivatives. I can give further data and formulas if required. The program is the easy bit but I just don't know how to get the write answers into Excel first so I can work out how to program it correctly.