Amy H.

asked • 04/14/17

Solve the equation on the interval [0, 360]

Solve the equation on the interval [0, 360°]. 2cos2(x)+5cos(x)-3=0

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Mark M. answered • 04/14/17

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2cos2(x) + 5cos(x) - 3 = 0
a = cos(x)
2a2 + 5a - 3 = 0

(2a - 1)(x + 3) = 0 {1/2, -3}

Now determine value of x.
 
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Doug C.

I get 1/2 or -3 for the possible values of a. 
 
Since cos x cannot equal -3, you are left with finding all values of x (between 0 and 360) such that x= cos-1 1/2
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04/14/17

Mark M.

Thanks, you are correct. Must check my arithmetic!
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04/14/17

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