Question

Represent the following complex number in trigonometric form:
$-\sin \alpha -i\cos \alpha .$

Answer 1

$\frac{i(-\sin \alpha -i\cos \alpha )}{i}$

$⟹\frac{(\cos \alpha -i\sin \alpha )}{e^{i\pi /2}}$

$⟹\frac{e^{-i\alpha }}{e^{i\pi /2}}$

$⟹e^{-i(\frac{\pi }{2}+\alpha )}$