Question

Express the complex number in trigonometric form.

-2i

A) 2(cos 180° + i sin 180°)

B) 2(cos 90° + i sin 90°)

C) 2(cos 270° + i sin 270°)

D) 2(cos 0° + i sin 0°)

Answer 1

The point 2 units along the -i axis is at an angle of 270° from the +real axis. Hence the best choice is ...
C) 2(cos(270°) +i·sin(270°))