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Cos^2x -Sin^2x+3Sinx-2=0  |Cos^2x = 1-sin^2x
1-Sin^2x -Sin^2x+3Sinx-2=0
 -2Sin^2x + 3sinx - 1 = 0
factoring
 (-2Sinx +1)(Sinx - 1) = 0
  (-2Sinx +1)=0
     Sinx = 1/2  x = pi/6, 5pi/6
  (Sinx - 1) = 0
     Sinx  = 1   x =  pi/2