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Angle x is a third quadrant angle such that cosx=−2/3 .

What is the exact value of cos(x/2) ?

Answer in simplest radical form

 Mar 26, 2020
 #1
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cos x = -2/3

 

Since x  is  in  Q#, then (x/2)  will lie  in Q2  .....and the cosine is negative there....so.....

 

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

 

- √6 / 6

 

 

cool cool cool

 Mar 26, 2020

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