SOLUTION: if cos x= -1/4 and pi/2 < x < pi, find the value of sin(x/2)

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Question 333083: if cos x= -1/4 and pi/2 < x < pi, find the value of sin(x/2)
Answer by Tutorteddy.Com(12) About Me  (Show Source):
You can put this solution on YOUR website!
cos x = 1 - 2sin^2(x/2)
=> sin^2(x/2) = (1 - cosx)/2 = (1 + 1/4)/2 = 5/8
=> sinx/2 = Sqrt(5/8) = [sqrt(5/2)]2
The negative value is discarded as pi/2 < x < pi and sinx is positive in this quadrant.