SOLUTION: what are all the solutions of 2cos^2(x)-cos(x)-1=0 that lie in the interval [0, 2pi]

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Question 561942: what are all the solutions of 2cos^2(x)-cos(x)-1=0 that lie in the interval [0, 2pi]
Answer by solver91311(24713) About Me  (Show Source):
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Do a simple substitution. Let

Then



It factors



So



or



Hence



or



So



or



Find these values on the unit circle:



bearing in mind that the cosine is represented by the -coordinate of a point on the unit circle and don't miss the fact that your given interval is inclusive of BOTH end points.

John

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