Need Some Math Help

[KEDA]

Joe used his abacus to figure out how much it was.

[Fillmoe]

verizon should hire randall patrick munroe

[baseline bum]

Crap, that's Euler's law. I'm a EE major, I'm supposed to know that.

You should get to know it well, because the formulas:

sin(x) = (e^(ix)-e^(-ix))/(2i)

and

cos(x) = (e^(ix) + e^(-ix))/2

are two of the most useful things for doing any kind of trig problem (especially in problems involving angle addition), and they come up all the time in PDEs and ODEs.