General formulas:
\[ z = a + i b \quad \Longrightarrow \quad r = \sqrt{a^2 + b^2}, \quad \theta = \arg(z) \]with \( -\pi < \theta \le \pi \) (principal value). Then:
\[ \text{Polar: } z = r\big(\cos\theta + i\sin\theta\big) \] \[ \text{Exponential: } z = r e^{i\theta} \]* Principal argument: -π < θ ≤ π (-180° < θ ≤ 180°).