Find the exact value of the indicated trigonometric function?

cosX = 2/9 tanX < 0 Find sinX

This is the only question I don't remember, if you could also please show the steps so I can understand it that would be awesome, Thank you

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  • 8 years ago
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    Given that cosine is positive and tangent is negative tells us we are in quadrant 4, using CAST rule

    recall SOHCAHTOA that COSx = A/H so adj is 2 and hyp is 9. Use Pythagorean theorem to find third side of the triangle (opposite)

    9^2 - 2^2 = 77, so opposite side is root(77)

    so SinX = - root(77) / 9 [negative because of the quadrant, in that the opposite is in the down direction]

    Source(s): math teacher
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