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Math Help - trig equations help

  1. #1
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    trig equations help

    solve the following equations in the given interval.

     \tan(3x+25) = -0.51  -90< x \leq 180
    Last edited by Tweety; April 19th 2009 at 08:31 AM.
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  2. #2
    No one in Particular VonNemo19's Avatar
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    formulas!

    Try looking at your addition formulas and the problem doesn't seem so tough any more. I could solve it for you but that wouldn't be any fun!
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  3. #3
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    Quote Originally Posted by VonNemo19 View Post
    Try looking at your addition formulas and the problem doesn't seem so tough any more. I could solve it for you but that wouldn't be any fun!
    I dont know what the addition formula is, Have not been taugh that yet.

    heres my working but I dont seem to get the right answers.

     \tan(3x+25) = -0.51

     X = 3x+25

     tanX = -0.51

     tan^{-1} (-0.51) = -27.02

     -90< x \leq180

     -270< 3x \leq540

     -245< 3x+25 \leq 565

    As tanX is −ve, X is in the 2nd and 4th quadrants

    so the solutions between −245<X ≤ 565

    should one of the solutions be 27 ?

    also;

    in the fourth qudrant = 360-27 = 333

    second quadrant = 180-27 = 153

    but I have to get all the solutions up to 565 , how do I do that ?



    The correct answer are; X= −207, −27, 153, 333, 513,
    can you explain how they get -27, -207 and 513 from ?
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