Concept of Rotation – As multiplying a complex number by $e^{i\alpha}$
Let $Z = r.e^{i\theta}$ is a non zero complex number where $r=\vert Z \vert $ and $\theta = arg(Z)$.
$\therefore$ when we multiply $e^{i\alpha}$ to Z we get a complex number Say $W=Ze^{i\alpha}=r.e^{i(\alpha + \theta)}$
$\therefore$ Geometrically $Z.e^{i\alpha} = W$ can be obtained by rotating OA in anticlockwise direction by an angle $\alpha $ , which is also called as the concept of rotation .
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