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