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Angle x is a third quadrant angle such that cosx=−1/5 .

What is the exact value of cos(x/2) ?

Enter your answer, in simplest radical form, in the box.

cos(x/2) =

 Apr 2, 2020
 #1
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cos (x / 2)  will  be  a Q2  angle if  x  is in Q3.....so....cos (x /2 )  is negative  ...so

 

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

 

- 2√ 10 / 10   =

 

- √ 10  /  5

 

 

cool cool cool

 Apr 2, 2020

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