SOLUTION: If cos theta equals -4/9 with theta in quadrant 2, find sin theta.

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Question 1033489: If cos theta equals -4/9 with theta in quadrant 2, find sin theta.
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
If cos theta equals -4/9 with theta in quadrant 2, find sin theta.
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sin = sqrt(1 - cos^2) = sqrt(1 - 16/81)
sin = sqrt(65)/9
sine is positive in Q2

Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
.
If cos theta equals -4/9 with theta in quadrant 2, find sin theta.
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sin%28theta%29 = +sqrt%281+-+cos%5E2%28theta%29%29 = sqrt%281-%28-4%2F9%29%5E2%29 = sqrt%281+-+16%2F81%29 = sqrt%28%2881-16%29%2F81%29 = sqrt%2865%2F81%29 = sqrt%2865%29%2F9.

The sign is "+" since theta is in quadrant 2, where sine is positive.