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Math Help - Minimum distance point proof for triangle with one angle >= 120

  1. #1
    Junior Member hercules's Avatar
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    Minimum distance point proof for triangle with one angle >= 120

    Hello,

    I am having a little trouble developing a proof for the minimum distance point in the following scenario.

    if i have a triangle with vertices A, B, and C.
    measure of angle ABC is >=120 degrees
    prove that the vertex B is the minimum distance point?

    if there was another point call it P, then the distance from P to the vertices of the triangle which is
    PA + PB + PC is greater than the distance from vertex B which is AB + BB+ BC = AB + BC.
    That is saying that vertex B of triangle is the minimum distance point.

    You might want to look at Fermat point.

    Please help me construct a proof for this case.

    Thank You
    Last edited by hercules; July 13th 2009 at 06:48 PM.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by hercules View Post
    Hello,

    I am having a little trouble developing a proof for the minimum distance point in the following scenario.

    if i have a triangle with vertices A, B, and C.
    measure of angle ABC is >=120 degrees
    prove that the vertex B is the minimum distance point?

    if there was another point call it P, then the distance from P to the vertices of the triangle which is
    PA + PB + PC is greater than the distance from vertex B which is AB + BB+ BC = AB + BC.
    That is saying that vertex B of triangle is the minimum distance point.

    You might want to look at Fermat point.

    Please help me construct a proof for this case.

    Thank You
    did the solution i suggested work out for this?
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  3. #3
    Junior Member hercules's Avatar
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    Quote Originally Posted by Jhevon View Post
    did the solution i suggested work out for this?

    Yes, it did. We didn't even need to calculate the length using sine values
    Since our triangle PBP' was isosceles by construction. We had only to realize that as the vertex angle decreased (which we found to be restricted between 0 and 60 degrees) the length of the base PP' also decreased.

    Sorry, for the delayed response. I found math forum mail filtered.
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