Question

Express the complex number in trigonometric form.
-2
i gather it has to be one of these 4...
2(cos 90° + i sin 90°)

2(cos 0° + i sin 0°)

2(cos 180° + i sin 180°)

2(cos 270° + i sin 270°)

Answer 1

it is 2cos (pi). we don't have i sin (pi) because sin(pi) =0.