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Math Help - Least squares method problem!

  1. #1
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    Question Least squares method problem!

    Hy everyone. First, Im sorry if I missed subforum. Please help me about this problem of least squares method. I solved first part of problem when you have to do least square method, but I dont understand how to put triangle in that coordinate system and calculate area of it. my online calculation of l.s.m is here -> http://i46.tinypic.com/okvssn.jpg

    Problem -> With the method of least squares find best line f(x) which goes through six given points from A to F. Calculate area of triangle bounded with that line, and axis X and Y.

    Points are : A ( 18.6 , -143.8 ) ; B ( 29.5 , -250.2 ) ; C (32.5 , -278.3 ) ; D ( 41.5 , -365.8 ) ; E ( 54.5 , -490.9 ) ; F ( 62.9 , -575.5 )
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  2. #2
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    Re: Least squares method problem!

    Quote Originally Posted by danijelrd View Post
    Hy everyone. First, Im sorry if I missed subforum. Please help me about this problem of least squares method. I solved first part of problem when you have to do least square method, but I dont understand how to put triangle in that coordinate system and calculate area of it. my online calculation of l.s.m is here -> http://i46.tinypic.com/okvssn.jpg

    Problem -> With the method of least squares find best line f(x) which goes through six given points from A to F. Calculate area of triangle bounded with that line, and axis X and Y.

    Points are : A ( 18.6 , -143.8 ) ; B ( 29.5 , -250.2 ) ; C (32.5 , -278.3 ) ; D ( 41.5 , -365.8 ) ; E ( 54.5 , -490.9 ) ; F ( 62.9 , -575.5 )
    I'll assume that the LS line from your jpeg is correct: y = -9.71801194177x + 37.1606433422.

    From here, take one of two avenues:

    First Method: Calculus

    The area of the triangle is the area under the curve (LS line, in this case) bounded from below by the Y-axis ( X=0) and from above by the X-axis ( y=0). The lower X-limit is 0 and the upper X-limit is the solution to 0 = -9.71801194177x + 37.1606433422, which is \tfrac{37.1606433422}{9.71801194117}\approx 3.82389356638635.

    \int_{x=0}^{x=3.82389} -9.71801x + 37.16064 = (-\tfrac{9.71801}{2}x^2 + 37.16064x)|^{3.82389}_{0} \approx 74.049

    Second Method: Find the triangle's coordinates, compute the area of the relevant rectangle, then take half that number. That is, \frac{b\cdot h}{2}.
    Thanks from danijelrd
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  3. #3
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    Re: Least squares method problem!

    Thank you very much for answer!! ))
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