Question 920116
2(1-cos^2 x) + 9cos x = 6
2 - 2cos^2 x + 9cosx = 6
2cos^2 x - 9cosx + 4 = 0
(2cosx -1)(cosx - 4) = 0 (cosx = 4 Invalid)
cosx = 1/2
x = &#960;/3, 5&#960;/3
(cosx, sinsx) Summary Unit Circle for You Referecne
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