AC circuits is one of those places where one can have absolutely badass complex maths for really useful applications. Nyquist stability, yumm! The analytical properties of amplifier response functions in the complex frequency plane telling you whether the amp is stable? That's just cool shit.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition