There are tools to do most of the trig. There's one in MaGUI, and a cardboard one you can make. The tutorial is here:
http://www.subsim.com/radioroom/show...6&postcount=38
It's for SH5, but the method and the map tools are the same. It really works!
Also, check here
http://www.gamefront.com/files/user/joegrundman. In the documentation is a step-by-step description of a passive-sound-only attack tactic that really works! It's less math-intensive than the classic 4-bearing method, but operationally sound. I don't know if any U-boat skippers actually used this exact technique, but they could have.
But, yeah, come to think of it, there is a lot of trig here, either intuitive or calculated. That was the nature of the fire control problem and of ship maneuvers in WW2. I never thought I would be using a moboard in a game, but it's helpful, because those are the problems that keep coming up. What we get when we ask for "realism."