Trig and calculus are IMHO at least useful, and trig comes from geometry, so....

You will absolutely need complex numbers, so at least the beginnings of vector spaces.

AC networks are hard to really understand without trig, and phasors are much easier to understand once you really get Eulers identity (Which comes from Complex analysis and finite dimensional vector spaces).

Matrix methods are sometimes by far the easiest way to solve a network, which is where linear algebra and Gauss Jordan elimination come in.

The Lapalace transform is profoundly useful for making systems of differential equations more tractable (There are simple geometric rules about pole/zero locations that tell you useful things about stability), which (Like the Fourier transform) comes from basis functions.

It is less about being able to do the maths day to day (I would have to hit the books to remember how to integrate F(x)G(x) between limits these days), as being able to recognise what is going on.

One thing to make sure is that you have the fundamentals down, it is amazing how missing some little piece of basic maths can make things very, very confusing in a later class.

Stats is something I must get better at, but sometimes even the little I do know is very useful.

For doing the mathematics in the real world, we have computers, but recognising the required maths for a given desired result, that is still a human task.

Regards, Dan.