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Math Help - Why not negative?

  1. #1
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    Why not negative?

    How should I know not to use a negative value after taking a square root? In the question I might have thought cos x=-(4/5) and sin x=-(3/5).
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  2. #2
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    Quote Originally Posted by Stuck Man View Post
    How should I know not to use a negative value after taking a square root? In the question I might have thought cos x=-(4/5) and sin x=-(3/5).
    Look at the domain x which in this case is the first quadrant.

    What is the sign of sine and cos here?
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