Question

Find the solution of the following equation whose argument is strictly between 90° and 180°.

Answer 1

Answer:

180degreesStep-by-step explanation:

Given the complex value

z² = -81i

z = (-81i)^1/2

Get the argument of -81i

theta = arctan(y/x)

theta = arctan(-81/0)

theta = -90degrees

theta = -π/2

Since tan is negative in the secind quadrant

theta =  π - π/2

theta = π/2

According to demoivres theorem

theta = 1/2 * π/2

theta = π

theta = 180degrees