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Math Help - Missing parts of triangle

  1. #1
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    Missing parts of triangle help

    How in the world do I find the missing parts of the triangle ABC if a = 12, b = 19, and A = 82 deg's?


    Thanks very much
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  2. #2
    Site Founder Math Help's Avatar
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    Lightbulb Law of sines


    ////a/
    /.\
    ////a/\.\\b
    a//./____\
    .........
    c

    a = 12, b = 19, and A (opposite a) = 82 deg's

    remember that \frac{a}{sinA}=\frac{b}{sinB}=\frac{c}{sinC}

    now you can easily solve for B.

    Once you have B you know that A+B+C = 180 so you can get C and finally use C and the law of sines to get c

    let me know if you need more help
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  3. #3
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    Please Help!!!!

    For angle B I get SinB = 19sin82deg / 12 which gives me 1.5679 and when I do arcsin 1.5679 I get an Error why is this?
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  4. #4
    Site Founder MathGuru's Avatar
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    Ambiguity in the stated question

    The reason is that the problem is not clearly stated. There is no way that the angle opposite a is 82 degrees. It can only be between a and b (I would have called that angle C as it is opposite c) Try it again this way and you will get the answer.
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  5. #5
    Site Founder MathGuru's Avatar
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    I just realized Angle B could also be 82 degrees so you have to figure out which angle it is talking about.
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