think I would have to go drag out my old engineering maths book and brush up on calculus and trig eeeeek
used to quite like euler equations of the form "e^j theta" and proving from first principles. 6 pages of calculus later . . . .
Don't ask me now as I would not have a clue!
we had this funny little Indian maths professor called Kash Dev who showed us all sorts of little shortcuts and tricks. Funny little bloke but man very switched on. Can still hear his voice . . . "we take e de power j theta . . ."