**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** .

https://www.mathsdiscussion.com/wp-content/uploads/2019/12/test-note-1.pdf

For more such articles helpful for IITJEE preparation check her ( IITJEE )