# How do you express the complex number in trigonometric form: -2?

Apr 29, 2016

$2 \cos \pi + i \sin \pi$.
A real number has the argument equal to zero if positive or $\pi$ if negative:
So, it is $2 \cos \pi + i \sin \pi$.
$\sin \pi = 0$ so number is real;
$\cos \pi = - 1$ so the number is negative.