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Math Help - perimeter of a triangle

  1. #1
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    perimeter of a triangle

    Could someone please help me figure out where to start to get the answer to this?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sanee66 View Post
    Could someone please help me figure out where to start to get the answer to this?
    use the distance formula to find the length of the sides. then just add them together.

    recall, the distance formula, that is, in this case, the formula for the length of a line is:

    d = \sqrt {(x_2 - x_1)^2 + (y_2 - y_1)^2}

    do you think you can continue now?
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  3. #3
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    perimeter of a triangle

    I come up with 232. Would this be right?
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sanee66 View Post
    I come up with 232. Would this be right?
    hmmm. i got 25.502. i'm not sure how you managed to get that.

    triangle DEF has three sides: DE, EF and DF.

    we have: D(-4,6) \mbox { , } E(5,3) \mbox { , } F(3,-2)

    So, the length of DE is:

    DE = \sqrt {(5 - (-4))^2 + (3 - 6)^2} = \sqrt {90}


    the length of EF is:

    EF = \sqrt {(3 - 5)^2 + (-2 - 3)^2} = \sqrt {29}


    the length of DF is:

    DF = \sqrt {(3 - (-4))^2 + (-2 - 6)^2} = \sqrt {113}


    The perimeter is the length of all the sides, therefore

    Perimeter = \sqrt {90} + \sqrt {29} + \sqrt {113} \approx 25.502
    Last edited by Jhevon; June 13th 2007 at 06:47 PM.
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  5. #5
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    Thumbs up perimeter of a triangle

    i was weird and took x1-x2 and y1-y2 instead of the other way around. Thanks for all your help.
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  6. #6
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    Quote Originally Posted by sanee66 View Post
    i was weird and took x1-x2 and y1-y2 instead of the other way around. Thanks for all your help.
    It makes no difference.
    Since you are squaring
    (y_1-y_2)^2 = (y_2-y_1)^2
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