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Math Help - lighthouse

  1. #1
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    lighthouse

    a lighthouse is 10 miles northwest of a dock. a ship leaves the dock at 9 am and streams west at 12 miles per hour. At what time will it be 8 miles from the lighthouse?

    use law of cosines
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  2. #2
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    Quote Originally Posted by aeroflix View Post
    a lighthouse is 10 miles northwest of a dock. a ship leaves the dock at 9 am and streams west at 12 miles per hour. At what time will it be 8 miles from the lighthouse?

    use law of cosines
    have you made a sketch? probably the most important thing you can do to solve this problem.

    the closest distance to the lighthouse will be a bit over 7 miles ... it will be a distance of 8 miles from the lighthouse at two different times.
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  3. #3
    Senior Member Educated's Avatar
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    Quote Originally Posted by aeroflix View Post
    use law of cosines
    From the picture that I have formed, I would think using the sine rule would be better.
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