Verified answer

sin (4Ө) = - √3 / 2

4Ө = 240° ,300° ,600° ,660° ,960° ,1020° ,1320° ,1380°

Ө = 60° , 75° , 150° , 165° , 240° , 255° , 330° , 345°

2sin4Θ + √3 = 0? solve in the interval of [0, 2π) or [0, 360 degrees)

sin4theta = -sqrt(3)/2 = -0.8660

so theta will lie in the 3rd and 4th quadrants, i.e. between 180 & 270 and 270 & 360 degrees

4theta = -60 degrees

theta = -15 degrees

theta = 195 and 345 degrees

---------------------------------------