What is the exact value of cos (x/2)? Enter your answer, in simplest radical form, in the box. cos (x/2) = ___

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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 the simpliest radical form

Use the fact that \(cos(x)=2cos^2(x/2)-1\)