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Thread: find an angle

  1. #1
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    milan
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    find an angle

    Hi! I have a trig problem.

    find an angle-immagine.jpg

    What we know:
    AB = 12 mm
    CD = 6 mm
    DA = 20 mm
    ABC = 110
    BCD = 130

    What I would like to know:
    DAB = ?

    Thanks a lot in advance for any help!

    Regards
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  2. #2
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    Lebanon
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    Re: find an angle

    angle DAB \approx 50.48{}^{\circ}
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  3. #3
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    milan
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    Re: find an angle

    Thanks but did you determinate it algebraically? How?
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  4. #4
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    Re: find an angle

    find an angle-quad.jpg

    Law of sines in triangle ABE and again in triangle DCE

    \frac{\sin  E}{6}=\frac{\sin  50^{\circ }}{d}

    \frac{\sin  E}{12}=\frac{\sin  110^{\circ }}{d+20}

    where d = ED
    Thanks from skeeter
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