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Angle x is a third quadrant angle such that covers cos x = -2/3. What is the exact value of cos(x/2)? Enter your answer, in simplest radical form, in the box. cos(x/2) = ___

 May 1, 2020
 #1
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Since x lies in Q3......then x/2 will fall into Q2...so....the cosine is negative there

 

cos (x/2)  =  -√ [  (1 + cos x)  / 2 ]

 

cos (x/2)  =  - √ [ ( 1 - 2/3 ) / 2 ]   =   - √ [ 1/6]  = - √6 / 6

 

 

cool cool cool

 May 1, 2020

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