Jika sin^2x - 2cosx = 1 dimana 0

2sin²x + 3cosx = 0
2(1-cos²x) + 3cosx = 0
2 - 2cos²x + 3cosx = 0
2cos²x - 3cosx - 2 = 0
(2cosx+1)(cosx-2) = 0
(2cosx+1) = 0 
2cosx = -1
cosx = -1/2
⇒cos x = cos 120°
         x = 120°
⇒cos x = cos 240°
         x = 240°