Oh, I had finished complex numbers (not [STRIKE]complex analyse[\STRIKE])
appears frequently in the texts of ??electronic?? ??circuit??.
I'm ready for ??electronic?? ??circuit?? but I don't know even the topic name.
in electrical engineering the symbol j is commonly used instead of i, to denote a square root of -1.
t is a parameter, used thought of as "time elapsed". is a function which sweeps out a circle in the complex plane, as time passes.
it can be thought of as a "paired function of time", where the x-coordinate is cos(wt), and the y-coordinate is sin(wt), and w is the frequency.
often, the value one is interested in, is just the "real part" (the cosine), but considering the "real parts" and "imaginary parts" as bound,
often calculations regarding oscillators are greatly simplified, especially with regard to "phase shift".
while i don't know any texts off-hand that would be a good fit for you (try searching amazon.com for "complex numbers for electrical engineers")
you might take a look at this web-site: Table of Contents