Question

Can someone help pleaseee​

Answer 1

Explanation:

7-3cosx=9sin²x

[sin²x=1-cos²x]

=>

7-3cosx=9-9cos²x

=>

9cos²x-3cosx-2=0

=>

let cosx=t

9t²-3t-2

by quadratic formula,

t=(3±9)/2·9

=> t=2/3 or t=-1/3

thus,

x=acos(2/3) or x=π- acos(1/3)