Please help!

cot (2ɵ/3)= - square root of 3

cot (2ɵ/3)= - square root of 3

or
tan (2ɵ/3) = -1/√3
so (2ɵ/3) is in the 2nd or 4th quadrants
we know tan pi/6 = + 1/√3

so (2ɵ/3) = pi - pi/6 = 5pi/6
2ɵ = 5pi/2
ɵ = 5pi/4
or
(2ɵ/3) = 2pi - pi/6 = 11pi/6
ɵ = 11pi/4