function and function

Discussion in 'Physics & Math' started by f.point, Mar 11, 2015.

  1. f.point Registered Member

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    5
    On the x-coordinate, there is straight line AB, point A is fixed on the x-coordinate, point B is located at any point x-coordinates, to describe this function.
     
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  3. James R Just this guy, you know? Staff Member

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    I don't understand your question.
     
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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Perhaps he has a typo. Near the end meant to say:
    "... point B is located at any point y-coordinates,...

    Answer to question he asked is: y=0 for all x such that A<x<B plus point A & B if you want them included on the Line segment.
     
    Last edited by a moderator: Mar 12, 2015
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  7. f.point Registered Member

    Messages:
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    no , point B is located at any x-coordinate

    solutions :
    point A=a , point B=x , y=AB

    a) y=|a-x|

    b) y=-|a-x|

    c) y=a-x

    d) y=x-a

    Mathematics official says geometric objects measures must be positive numbers, say my function to geometric objects measures may be negative numbers


    question - how to make it look proceedings graphics of my functions in the plane (Cartesian coordinate system)
     
  8. origin Heading towards oblivion Valued Senior Member

    Messages:
    11,890
    Answer: A line on the x axis means that for any x, y=0.
     
  9. f.point Registered Member

    Messages:
    5
    This is the function point (A - is a constant, B - is a variable) length of straight line (AB) is the solution functions
     
  10. origin Heading towards oblivion Valued Senior Member

    Messages:
    11,890
    Then you mean:
    |a - b| = x
    y = 0
    z = 0
     
  11. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    23,198
    I doubted anyone asking, especially so poorly that James could not guess what the question was, would know either that vertical bars indicate absolute value or that is always a non-negative difference, and this form is some what ambiguous about the status of his points A & B (part of the line segment or not?)

    But worse is you have defined a single point at (|a- b|, 0, 0) in standard Cartesian coordinates, not a line segment, and that point may not even be on the line segment he wanted defined!

    I think you really mean: |a-b|> x for a < x < b , which will at least let x have various values, but that is not as clear or simple as the form I gave.
     
    Last edited by a moderator: Mar 13, 2015
  12. origin Heading towards oblivion Valued Senior Member

    Messages:
    11,890
    Yeah, a-b is the length of the line segment it is not x as I stated. I was trying (incorrectly) to have him understand that he is describing a line on the x axis so there is no y or z component.
     
  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Messages:
    23,198
    Yes. that is exactly what I said in post 3:
    "Answer to question he asked is: y=0 for all x such that A<x<B"
    It really does not get more simply and clearly stated than that bold part.
     
  14. Secret Registered Senior Member

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    299

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    Seemed to be a family of line segments that has one of its endpoints located on the line x=a
    Since there is nothing said about the coordinates of point A and point B, assume they can take any y values in reals

    Let A=(a,y1), B(x,y2) with x, a, y1, y2 in reals and a fixed. Let (x',y') be a point on the function

    The required function is
    Domain: x' in [a,x]
    Codomain y' in [y1,y2]

    (y2-y1)/(x-a)=(x'-a)/(y'-y1)
    (y2-y1)(y'-y1)=(x'-a)(x-a)
    y2y'-y1y'-y2y1+y1^2=x'x-ax-x'a+a^2

    y'(y2-y1)+x'(a-x)+(y1^2-a^2+ax-y2y1)=0 ------(*)

    which is a straight line segment with endpoints A and B for any y1,y2,a,x

    The length of each line segments in the family is then
    l=sqrt((y2-y1)^2+(x-a)^2)

    Interesting cases of (*)
    1. When y1=y2=c (c in reals)
    (*) is the horizontal line segment [a,x] at y=c
    When c=0, (*) is the interval [a,x]

    2. When y2<y1 and a<x OR y2>y1 and a>x, the slope is negative, otherwise it is nonnegative
    In particular slope is zero when y1=y2=c as mentioned above and infinite when a=x

    3. When y1=y2 and x=a, you get a contradiction. I have not attempt to analyse the limit of (*) as y2 approaches y1 and x approaches a yet

    I am not sure if there are other interesting cases for (*), but it seems its length is never negative valued
     
  15. f.point Registered Member

    Messages:
    5
    there is only one y ( no y1,y2 )
    The mapping function from the x-coordinates of the plane (Cartesian coordinate system)
    y = x-a, x and a remain on the x-coordinate, y goes to the y-coordinate.
    view photo
    https://pkxnqg.bn1302.livefilestore...WSh5idkVdC-swrTkqYaXV8fmts9x7Ks/ii.png?psid=1
    the lines of x and a parallel to the y-coordinates
    line of y parallel to the x-coordinate
    formed at the intersection of real points A and B
    points A and B are combined and gets straight line AB
    is given by x = 4, a = 2, y = 2
    Repeat for x = 3.5, a = 2, y = 1.5, view photo
    formed at the intersection of real points C and D
    points C and D are combined and received straight line CD

    https://befwwg.bn1302.livefilestore...DKraCcJKIy-UHkR4VeCHL_PmPvJTSMeM/i.png?psid=1
    connect the dots AC (BD) straight lines AB and CD
    ABDC points form the surface of 4≥x≥3.5

    Draw a graph of the function at the current proceedings for

    a) y=|a-x|

    b) y=-|a-x|

    c) y=a-x

    d) y=x-a

    e) y={|a-x|}\cup{-|a-x|}
     
  16. danshawen Valued Senior Member

    Messages:
    3,951
    What you described is either a undirected line segment or an ideal point.

    A "function" would require at least two ordered pairs of coordinates to describe, even if such a description was "piece-wise" or discontinuous.
     
  17. f.point Registered Member

    Messages:
    5
    a) y=|2-x|
    graph, the red surface
    https://cfxpzq.bn1302.livefilestore...duf35TDz7kJFlvpinPGfiGmOhMAVbDw/01.png?psid=1

    b) y=-|2-x|
    graph, the red surface
    https://nq6hfq.bn1302.livefilestore...xhUjRvcF6i6WXHS-qNoA1O50MwSx-Kw/02.png?psid=1


    c) y=2-x
    graph, the red surface
    https://0nivia.bn1302.livefilestore...qqqkUyEXwbMEkel843ZQ20Rq__x6V-A/03.png?psid=1

    d) y=x-2
    graph, the red surface
    https://d6pekg.bn1302.livefilestore...0AJlHabqjfVBAgiGORjpymT7vzmMKCA/04.png?psid=1

    e) y={|2-x|}[LATEX]\cup[/LATEX]{-|2-x|} or y={2-x}[LATEX]\cup[/LATEX]{x-2}
    graph, the red surface
    https://qhdsnq.bn1302.livefilestore...HeXxWALY-BwcLW4G5ObhnQSYfKmEaVQ/05.png?psid=1

    which are geometric objects obtained for valuesx and y , shape a≥x≥b ( a≥y≥b ) ? , you have a graph
     

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