SOLUTION: cos2x = -cosx for 0 &#8804; x < 2pi: (Round to nearest tenth.)

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Question 1117289: cos2x = -cosx for 0 ≤ x < 2pi: (Round to nearest tenth.)
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
cos2x = -cosx
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if you mean cos(2x) = -cos(x)
2cos^2(x) - 1 = -cos(x)
2cos^2(x) + cos(x) - 1 = 0
(2cos - 1)*(cos + 1) = 0
cos(x) = -1
x = pi
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2cos(x) - 1 = 0
cos(x) = 1/2
x = pi/3, 5pi/3