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Angle x is a third quadrant angle such that cos x = -1/5. 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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cos (x/2)  =  -√ [ (1 + cosx) / 2 ]

 

cos (x/2)  = -√ [ (1 -1/5) / 2 ]   =  -√ [ 4/10]  =  -2 / √10  =    -2√10/10  =   -√10 / 5

 

 

cool cool cool

 May 1, 2020

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