Trigonometry was the last one I did well in, and was necessary to understanding AC waveforms. (My AAS degree is Electronics Engineering)
I did have some basic calculus, did fair to middlin'. Just give me the bleepin' formulas, I don't care how they were derived!
Couldn't "get into" calculus, but I loved trig. Boolean Algebra was a cakewalk, and I liked it.
It's funny, though, I haven't used an oscilloscope or a logic probe in years. "If error code is L152, replace circuit board X57" is the most I do now. A chimp could do it.