Trigonometry: What is the polar representation of z = – 4i?

Question

What is the polar representation of z = – 4i?

1) –4cis (–π/4)

2) –4cis (π/4)

3) 4cis (–π/2)

4) 4cis (π)

5) None of these

Answer 1

Hello Ash!

The polar representation of a complex number is on the form:

z = r*(cosθ + isenθ)

r = 4

We must find an angle that satisfy cosθ = 0 and sinθ = -1. This is satisfied for θ = -π/2.

Therefore 3)

Feel free to send any messages with doubts.

Best regards!