# SOLUTION: Find all values of x in interval [0, 2(pi)] that satisfy sin2(x)=cos(x). I am having a problem with this question. I am getting half of the values in the answer so I am missing

Algebra ->  Algebra  -> Trigonometry-basics -> SOLUTION: Find all values of x in interval [0, 2(pi)] that satisfy sin2(x)=cos(x). I am having a problem with this question. I am getting half of the values in the answer so I am missing       Log On

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 Click here to see ALL problems on Trigonometry-basics Question 587923: Find all values of x in interval [0, 2(pi)] that satisfy sin2(x)=cos(x). I am having a problem with this question. I am getting half of the values in the answer so I am missing something. Any help would be great!Answer by lwsshak3(6522)   (Show Source): You can put this solution on YOUR website!Find all values of x in interval [0, 2(pi)] that satisfy sin2(x)=cos(x). 1-cos^2x=cosx cos^2x+cosx-1=0 Solve for cosx by quadratic formula: a=1, b=1, c=-1 cosx=[-1±√(1-4*1*-1)]/2*1 cosx=(-1±√5)/2 cosx=(-1±2.236)/2 cosx=-1.618 (reject, cosx≥-1) cosx=.618 x≈.905 and 5.378 radians in quadrants I and IV where cos>0