We have: .The question comes in 3 parts. I have done parts (i), (ii).
(ii) If the roots of a cubic equation are:
determine the cubic expression, by expansion, with these roots.
Multiply .  and : .
We have: .(iii) in part (ii) of this question, where is measured in radians.
Determine the values of that satisfy the roots, given that
And we have three equations to solve:
. . . .