Question

Express the complex number -3i in trigonometric form.

Answer 1

Use the formula z=a+bi=|z|(cosθ+isinθ), with |z|=√(a²+b²), and tanθ=b/a

in this case, a=0, b=-3 so |z|=√0²+(-3)²)=3
tanθ=
`(-3)/(0)`, notice the denominator is 0, undefined, so the value of θ=π/2
Substitute the values of θ=π/2 and |z|=3. into the formula, you'll get 3(cos(
`( \pi )/(2)`)+isin(
`( \pi )/(2)`))

Answer 2

b. 3(cos 270° + i sin 270°)

Explanation:

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