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Find all solutions in the interval [0, 2π).
cos2x + 2 cos x + 1 = 0
 one year ago
 one year ago
Find all solutions in the interval [0, 2π). cos2x + 2 cos x + 1 = 0
 one year ago
 one year ago

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mgarcia634Best ResponseYou've already chosen the best response.0
cos^2 x+ 2 cos x +1=0
 one year ago

cwrw238Best ResponseYou've already chosen the best response.1
this is a quadratic equation which will factorise
 one year ago

StiwanBest ResponseYou've already chosen the best response.1
\[\cos²(x) + 2\cos(x) + 1 = (\cos(x) + 1)²\] Hence the roots are all x out of [0,2pi) for which cos(x) = 1. pi and pi
 one year ago

StiwanBest ResponseYou've already chosen the best response.1
Sorry, of course it's just + pi as there are no negative numbers in this interval
 one year ago

cwrw238Best ResponseYou've already chosen the best response.1
what about 0 as a solution?
 one year ago

mgarcia634Best ResponseYou've already chosen the best response.0
the answer choices are a) x=2pi B)x=pi c) x=pi/4, 7pi/4
 one year ago

cwrw238Best ResponseYou've already chosen the best response.1
are you sure you have the correct question is it cos 2x or cos^2 x ?
 one year ago

StiwanBest ResponseYou've already chosen the best response.1
It's B) x = pi as in my answer.
 one year ago

cwrw238Best ResponseYou've already chosen the best response.1
in that case the answer is as Stiwam said
 one year ago
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