Question

Express the complex number in trigonometric form: -4i

I think the answer is 4(cos 180 + i sin 180)

Answer 1

4(cos 270° + i sin 270°)

Explanation:

Answer 2

Since the sin term is imaginary and cos is real, you need an angle that makes cos=0 and sin -1. This is 270 degrees. So
-4i=4(cos(270)+isin(270))