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## Homework Statement

We have cosx = -5/6 in the third quadrant, and I solved for sin(x/2).

I did sin^2(x/2) = 1-cos(x)/2 --> I get to sin^2(x/2)= 11/12, and here's my question.

When rooting I should choose the negative value because sine is negative in the third quadrant right? But in my webwork, the answer is the positive one. Can anyone explain to me why this is?