we have cot x = - √ 3
⇒ tan x = - 1 / √ 3
.................(1)
as we know that tan (π - θ) = - tan θ and tan (2π - θ) = - tan θ
now from (1) we get
tan x = tan (5π / 6) and tan x = tan (11π / 6)
⇒ x = 5π / 6 and x = 11π / 6
so the principal solutions are x = 5π / 6 and x = 11π / 6