You can put this solution on YOUR website! Find cosine theta, if sine theta = -2/5 in quadrant 3
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In QIII x and y are both negative.
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Since sine = y/r, y = -2 and r = 5
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Then x = sqrt[2^2+5^2] = sqrt[29]
So, x = -sqrt(29)
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Ans: cos(theta) = x/r = -sqrt(29)/5
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Cheers,
Stan H.
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