SOLUTION: Find all solutions in the interval [0,2pi) for the equation cos^2x + 2 cos x= -1

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Question 870963: Find all solutions in the interval [0,2pi) for the equation cos^2x + 2 cos x= -1
Answer by lwsshak3(11628) About Me  (Show Source):
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Find all solutions in the interval [0,2pi) for the equation
cos^2x + 2 cos x= -1
cos^2x + 2 cos x + 1=0
(cos x + 1)(cos x + 1)=0
cos x = -1
x = -π (multiplicity 2)