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Math Help - Conics-Circle Question

  1. #1
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    Conics-Circle Question

    To organize a military exercise, a drill sergeant designates an enemy territory represented by the inequality (x-2)^2+(y+5)^2 (less than or equal to 9) on the map of the base, whose axes are scaled in kilometers. If the soldiers respect a no man's land of 0.1km, what relation represents the friendly territory?

    Plz explain.
    THX in advance
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  2. #2
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    Quote Originally Posted by Solid8Snake View Post
    To organize a military exercise, a drill sergeant designates an enemy territory represented by the inequality (x-2)^2+(y+5)^2 (less than or equal to 9) on the map of the base, whose axes are scaled in kilometers. If the soldiers respect a no man's land of 0.1km, what relation represents the friendly territory?

    Plz explain.
    THX in advance
    The equation of a cirlce is

    (x-2)^2+(y+5)^2\le 3^2 where 3 is the radius of the circle

    If they respect no mans land it will incerase by .1 so the new equaition would be

    (x-2)^2+(y+5)^2 \le (3.1)^2
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  3. #3
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    well according to the answer booklet its 9.61. but why is that?
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    Quote Originally Posted by Solid8Snake View Post
    well according to the answer booklet its 9.61. but why is that?
    look at my above post again!

    (3.1)^2=....
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  5. #5
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    thx a million, sorry about my other post im a bit tired
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  6. #6
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    Quote Originally Posted by Solid8Snake View Post
    To organize a military exercise, a drill sergeant designates an enemy territory represented by the inequality (x-2)^2+(y+5)^2 (less than or equal to 9) on the map of the base, whose axes are scaled in kilometers. If the soldiers respect a no man's land of 0.1km, what relation represents the friendly territory?

    Plz explain.
    THX in advance
    Your inequality describes the area of a circle (circle line included) with the center C(2, -5) and the radius r = 3.

    If the soldiers keep a distance of more than 3.1 km to C then they are in the friendly area:

    (x-2)^2+(y+5)^2 > (3.1)^2
    Last edited by mr fantastic; May 18th 2009 at 01:49 AM. Reason: No edit. Just flagging this reply as having been moved from a thread containing duplicate question
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