If sin(?) = - 1/3 with ? in Quadrant III, what is cos(?)?

Question

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Answer 1

sqr(cos(x)) = 1 - sqr(sin(x)) = 1 - sqr(-1/3) = 1 - 1/9 = 8/9 in Quadrant III, both perpendicular and base are negative. cos(x) is negative. cos(x) = -sqrt(8/9) = -2*sqrt(2)/3