SOLUTION: If sine of theta equals -2/3 with theta in quadrant IV, what is cosine of theta? So.. y=-2/3 what does X=? Is it just Pythagorean identity? Like cosine of theta squared + s

Question 900902: If sine of theta equals -2/3 with theta in quadrant IV, what is cosine of theta?
So.. y=-2/3 what does X=?
Is it just Pythagorean identity?
Like cosine of theta squared + sine of theta squared = 1
And solve for cosine of theta ?
im not sure if im doing this right.
Found 2 solutions by Alan3354, stanbon:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
If sine of theta equals -2/3 with theta in quadrant IV, what is cosine of theta?
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sin^2 + cos^2 = 1
Solve for cos
Cosine is positive in Q4

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
If sine of theta equals -2/3 with theta in quadrant IV, what is cosine of theta?
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By definition, sin = y/r
So, y = -2 and r = 3
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Then x = sqrt[r^2-y^2] = sqrt[9-4] = sqrt(5)
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Ans: cos = x/r = sqrt(5)/3
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Cheers,
Stan H.
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