Diesel, Otto , Joule TRICK???

Hi Guys,
I try to callculate the efficiency for a cycle Process.
For Diesel, Otto and Joule Processes you can write the efficiency as a really small equation.

I have seen that for example sometimes the adiabatic equation is used,
but i don't understand in which case, or better, how I have to connect the procceses?

Is there a trick or do I have to learn it by memorization???

THX