Quadratic equations + trigonometry

First keep 6cosθ on one side and square the expression to get a quadratic in sinθ.From this evaluate sinα.sinβ.
Nxt keep the 8sinθ on one side and square to get a quadratic in cosθ.Find out cosα.cosβ.Now u can easily find out cos(α+β) and the n find sin(α+β)

well for this you have to be also careful about the sign of the answer, as given θ lies between 0 and 2π