Question

Express the complex number in trigonometric form.

-2

2(cos 90° + i sin 90°)
2(cos 180° + i sin 180°)
2(cos 270° + i sin 270°)

Answer 1

2(cos(180°) + i·sin(180°))

Explanation:

The point -2 in the complex plane is on the negative real axis. The angle that makes with the positive real axis is 180°. The point is 2 units from the origin, so the desired form of the number is ...

(units from the origin)(cos(angle) + i·sin(angle))

= 2(cos(180°) +i·sin(180°))