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DominiRican1013
 one year ago
Solve on the interval
[0,2π):
2cos2x+3cosx+1=0
DominiRican1013
 one year ago
Solve on the interval [0,2π): 2cos2x+3cosx+1=0

This Question is Closed

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0here we have to make this substitution: \[\cos \left( {2x} \right) = 2{\left( {\cos x} \right)^2}  1\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0so your equation, can be rewritten as follows: \[2\left( {2{{\left( {\cos x} \right)}^2}  1} \right) + 3\cos x + 1 = 0\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0what equation do you get?

DominiRican1013
 one year ago
Best ResponseYou've already chosen the best response.0I don't know I'm trying to work it out

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0hint: \[4{\left( {\cos x} \right)^2}  2 + 3\cos x + 1 = 0\]

DominiRican1013
 one year ago
Best ResponseYou've already chosen the best response.0I'll be right back.

DominiRican1013
 one year ago
Best ResponseYou've already chosen the best response.0I don't know how to do this.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0more explanation: we have: \[2\left( {2{{\left( {\cos x} \right)}^2}  1} \right) = 4{\left( {\cos x} \right)^2}  2\] am I right?

DominiRican1013
 one year ago
Best ResponseYou've already chosen the best response.0these are the choices \[A. x=2\pi, x=\pi/3\] \[B. x=\pi, x=2\pi/3, x=4\pi/3\] \[C. x=2\pi, x=\pi/4, x=5\pi/4\] \[D. x=\pi/6, x=7\pi/6\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0yes! I see them, nevertheless I can not give you the answer directly, since I have to respect the Code of Conduct

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.0If I simplify my equation above, I get: \[4{\left( {\cos x} \right)^2} + 3\cos x  1 = 0\] now, I make this substitution: cos(x)=y, so I can write: \[4{y^2} + 3y  1 = 0\] which is a quadratic equation. please solve that equation for y

DominiRican1013
 one year ago
Best ResponseYou've already chosen the best response.0B is the answer I got it
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