Question

For `z_1 = 9"cis" (5pi)/(6)` and `z_2 = 3"cis" (pi)/(3)`, find `(z1)/(z2)` in rectangular form.

a)-3
b)3
c)-3i
d)3i

Answer 1

3i

Explanation:

I did the work on paper to double-check the first person's answer and 3i is correct.

Answer 2

option D is correct, i.e. 3i

Explanation:

Given are the complex number as Z₁ = 9 cis(5π/6) and Z₂ = 3 cis(π/3)

So magnitudes are r₁ = 9, and r₂ = 3

And arguments are ∅₁ = 5π/6, and ∅₂ = π/3

We know the formula for division of complex number is given as follows:-

If Z₁ = r₁ cis(∅₁) and Z₂ = r₂ cis(∅₂)

Then |Z₁ / Z₂| = (r₁/r₂) cis(∅₁ - ∅₂)

|Z₁ / Z₂| = (9/3) cis(5π/6 - π/3)

|Z₁ / Z₂| = 3 cis(5π/6 - 2π/6)

|Z₁ / Z₂| = 3 cis(3π/6)

|Z₁ / Z₂| = 3 cis(π/2)

|Z₁ / Z₂| = 3 cos(π/2) + 3i sin(π/2)

|Z₁ / Z₂| = 3*(0) + 3i*(1)

|Z₁ / Z₂| = 0 + 3i

|Z₁ / Z₂| = 3i

Hence, option D is correct, i.e. 3i