Answer:
3(cos(75°) +i·sin(75°)) and 3(cos(255°) +i·sin(255°))
Explanation:
Using Euler's formula, this can be written as ...
x^2 = 9·e^(i5π/6)
Then the square roots are ...
x = (±√9)e^((i5π/6)/2) = ±3e^(i5π/12)
Of course, multiplying by -1 is the same as adding 180° to the angle.
The square roots are ...
3(cos(75°) +i·sin(75°)) and 3(cos(255°) +i·sin(255°))