Question 1138396: If theta is a third quadrant angle and cos theta = -2/3, find sin theta. Found 3 solutions by josmiceli, MathLover1, ikleyn:Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website! The sin is also negative in the 3rd quadrant
Find vertical coordinate
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Answer by MathLover1(20850) (Show Source): You can put this solution on YOUR website!
If theta is a third quadrant angle and , find .
From the sign on the cosine value, I only know that the angle is in QII or QIII. That's why they had to give me that additional specification: so I'd know which of those quadrants I'm in.
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The Pythagorean Theorem gives me:
=±
Since in QIII, below the x-axis, so y is negative.
I'll take the negative solution to the equation, and