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Math Help - Cosine/Sine Law?

  1. #1
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    Cosine/Sine Law?

    1.) A forty feet pole is braced by a wire from the top to a point 60 feet from its base up an 18 slope. How long is the wire? What angle does the wire makes with the ground?

    I'm confused about the question. I have no idea exactly how the diagram looks like so I cant figure out which of the sine/cosine law must be used. Please help, and if possible please show me how the diagram looks like. Thanks!
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  2. #2
    Super Member malaygoel's Avatar
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    I have drawn a figure
    Attached Thumbnails Attached Thumbnails Cosine/Sine Law?-.bmp  
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  3. #3
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    Quote Originally Posted by malaygoel View Post
    I have drawn a figure

    Could you please show the solution? I want to learn how to do it step by step. Thanks
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  4. #4
    Super Member malaygoel's Avatar
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    Consider triangle CDE
    ........given CD,DE and angle CDE

    cosine law:
    CE^2=CD^2+DE^2-2.CD.DE.cosCDE

    after CE is known,
    sine law:
    \frac{CE}{sinCDE}=\frac{CD}{sinCED}
    ...........hence angle CED can be determined.
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  5. #5
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    thank you

    thank you very much.
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  6. #6
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    You would learn better by trying first! Look at the triangle CDE. You know that side DE has length 60 feet, CD has length 40 feet, and you should be able to determine angle CDE (hint: CD is perpendicular to AF). Knowing those three parts if the triangle, use sine and cosine laws you refer to in your title to find the other parts.
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