Calculator test

[Johnh]

TBH, I've not seen complex numbers in 45 years of structural engineering. But I'm almost as equally interested in electronics, and for anything analogue, they are such an elegant and intuitive way of representing signals with phase that they are compelling. Even as basic a building block as a simple RC low pass or high pass filter only becomes fully clear with complex numbers
We are taught how the -3dB frequency (half power or about 1/sqrt2 voltage) happens when the capacitive reactance = the resistance. But plot it out on a complex plane and you can see it!