This "in-phase" effect can also be introduced by a phasing condition. Resistance in the complex domain is a real value which means there is no imaginary amount. Thus, since both current and voltage are in the same phase with each other, there will be no phase shift (θ = 0) between them.
So, the vectors of each value are presented in super-imposed mode and shown in the same reference axis. The transformation model from the phase format versus the sinusoidal domain of time can be derived in the next section.