First find sin (A/2)= +/-sqrt[(1/2)(1 - cos A)]
With A in the fourth quadrant, A/2 is in the second quadrant and sin A/2 is postive. Therefore
sin (A/2) = -sqrt[(1/2)(2/3)]
= sqrt(1/3)
csc (A/2) is 1/cos(A/2)= sqrt 3
check: A = 289.47 degrees
A/2 = 144.736 degrees
sin A/2 = 0.57735 = 1/(sqrt 3)
csc A/2 = sqrt 3
If cos A =1/3 with A in QIV find cscA/2
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