SOLVE: 2cos2x - 3cosx + 1 = 0 for for 0 is less than or equal to x is less than 2pi

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1 Answer

cos(2x)=2cos2(x)-1 so the equation can be rewritten:

4cos2(x)-2-3cos(x)+1=0,

4cos2(x)-3cos(x)-1=0=(4cos(x)+1)(cos(x)-1).

cos(x)=-¼ or cos(x)=1.

x=arccos(-0.25) or arccos(1),

x=1.8235 radians (104.48°) or 0 (in the given interval).

by Top Rated User (1.2m points)

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