Question 864123: If cos theta is 21/29 is quadrant 4 what's sin 2 theta?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! If cos theta is 21/29 is quadrant 4 what's sin 2 theta?
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By definition, cos(t) = x/r
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So x = 21 and r = 29
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In QIV, y is negative.
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So y = -sqrt[29^2-21^2] = -20
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Therefore sin(t) = y/r = -20/29
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Ans: sin(2t) = 2*sin(t)cos(t) = 2(-20/29)(21/29) = -0.9988
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Cheers,
Stan H.
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