Velocity derivative

Changing one velocity to another moves the location of a triangle on the time axis. The derivative of a triangle function is a box doublet. Thus to calculate a derivative with respect to velocity, it seems the main programming change to trimo() is to change ramp functions to step functions, i.e. to replace the call to doubint() by a call to causint(). The amplitude also changes by the scale dt/dv. It would be fun to continue here.