StrokesAk,
Don't worry Trig is actually pretty straight forward and very useful. I've just forgotten most of it, unfortunately (20 years since High School). I just thought it was funny that 20 years later I'm playing a game that actually got me digging through old books and doing math again!
It's funny how those dang story problems turn up in the oddest places!
This is all you need to find the lead angle to shoot the torpedo (for a 90 degree beam attack), provided you know y and x.
y = how far the CV will move in 4 minutes (the PT torpedoes run for 4 minutes then disappear)
x = how far the torpedo will move in 4 minutes