if cos theta = -4/5 for theta in quadrant 2, find sin theta/2
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In 2nd quadrant, sin x is +ve
cos x = -4/5
sin x = 3/5
cosx = 2cos^2(x/2) - 1
-4/5 + 1 = 2 cos^2(x/2)
-1/√10 = cos(x/2)
sin (x/2) = 3/ √10
cos x = -4/5
sin x = 3/5
cosx = 2cos^2(x/2) - 1
-4/5 + 1 = 2 cos^2(x/2)
-1/√10 = cos(x/2)
sin (x/2) = 3/ √10
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