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Homework Help: Optimization - gothic window

  1. Mar 29, 2010 #1
    1. The problem statement, all variables and given/known data
    a gothic window it to be built with 6 segments that total 6m in length. The window must fit inside an area that is 1m wide and 3 meters tall. the triangle on top must be equilateral. What is the maximum area of the window.


    2. Relevant equations



    3. The attempt at a solution
    so i made each of the sides of the trianle x and the width at the bottom of the rectangle x, then the sides of the rectangle equal to y. so the perimeter is 6=4x+2y
    and the area A=1/2xh + xy
    the height of the triangle would be 3-y wouldnt it? because then i plugged that in for h, and then isolated for y in the perimeter equation and plugged in y where it was necessary but i didnt get the right answer in the end after i got the derivative
     
  2. jcsd
  3. Mar 29, 2010 #2

    Dick

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    Science Advisor
    Homework Helper

    No, you don't know h=3-y. Given your perimeter constraint the maximum area window might not touch all sides of the 1m by 3m area. All you really know is that x<=1 and y+h<=3. What is true that h is related to x just because x is the side of an equilateral triangle and h is the height.
     
  4. Mar 30, 2010 #3
    I'm assuming your shape is like this?

    Code (Text):

    [u]/\[/u]
    |_|
     
    Since the top has to be an equilateral triangle you know that 3 segments have to be equal (if the base of the triangle counts as a segment). Then you have 3 segments left over to play with (the sides below the triangle and the base of the window)
     
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