Mark M. answered 04/27/20
Retired Math prof with teaching and tutoring experience in trig.
sin(2x) = -√3/2
2x = 4π/3 + 2kπ or 5π/3 + 2kπ, where k = 0, ±1, ±2, ...
x = 2π/3 + kπ, or 5π/6 + kπ
If k = 0, then x = 2π/3 or 5π/6
If k = 1, then x = 5π/3 or 11π/6
Other choices for k give values of x that are either larger than 7 or less than 0.