Compilation Of all -
Complex numbers are mainly used in electrical engineering techniques all the time, because Fourier transforms are used in understanding oscillations and wave behaviour that occur both in AC Current and in modulated signals.
Two-dimensional problems involving Laplace's equation (e.g. heat flow, fluid flow, electrostatics) are often solved using complex analysis, in particular conformal mapping
Complex numbers are used in real world literally EVERYWHERE.
Complex analysis (transformation or mapping) is also used when we launch a satellite and here on earth we have z-plane but in space we have w-plane as well. So to study various factors we use transformation.