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Thread: Graphing by hand

  1. #1 Graphing by hand 
    Forum Freshman
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    You know, I have a question -

    When you have system of equations, do you really have to have the same numbers on x-axis and y-axis? Let me give you an example -

    35 |
    30 |
    25 |
    20 |
    15 |
    10 |_____________________
    10 15 20 25 30 35

    So, instead of that, can you make the numbers on y-axis like 10, 20, 30, 40, 50 when x-axis leaves with 10, 15, 20, 25? Would that be ok or wrong? I mean, especially when you have the very high number of point of intersection of y? For example, you got 1925 of y and 150 of x. Can you put the numbers of 100, 200, 300 from the starting point, leaving with 10, 15, 20, 25 on x-axis like this?

    Thanx, just dont wanna get confused


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  3. #2  
    Forum Masters Degree bit4bit's Avatar
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    Its fine to use a different scale on different axis, the only affect will be that the graph is 'stretched' or 'squeezed' in that direction. Also, usually (but not always), the intervals are equidistant for a given axis (constant difference between steps), and they both start at (0,0)...the origin.


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  4. #3  
    Forum Freshman +SCIENCEgirl+'s Avatar
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    If you're interested:
    It is also okay to start for example at the x-axis by a high number.
    I'll explain by using your example:

    35 |
    30 |
    25 |
    20 |
    15 |
    10 |_____________________
    0 250 300 350 400 450

    if you're only interested in the interval <250, 450> you don't have to start at 50.. 100 etc

    it is commen to draw sometinhg at the beginning of the axis to show that. It looks like a heartbeat-thingie
    I've found an example:
    + Don't walk where the path may lead, walk instead where there is no path, and leave a trail...+
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  5. #4  
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    Very well.

    Thank you very much for the examples and explanations. Confusion's cleared much more now. Based on this subject, I've a question only left -

    Okay, I have put down the numbers on x axis, starting at 100 and on y-axis, starting at well, 500 or 1000, and the problem is - when I have lined out the dots, connecting to the point of intersection, like (150, 1925) I dont remember but it something like that, so when I have done lining both lines, what about the table of values?

    Table of values that is, when I've checked and some of the numbers in it don't really connnect together on a graph except the lines I'd drawn do connect to the right point of intersection properly. Should I ignore the numbers in the table of values?

    Again, thanks.
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  6. #5  
    Forum Freshman +SCIENCEgirl+'s Avatar
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    I think you mean that you made a table first, and then drew the graph?

    and you picked some values out of the table (including the point of intersection) and drew them into the graph?

    when you draw it by hand, it is really hard to draw the graph perfectly. so it will happen some times that there are some point in the table who don't lie on the graph .
    if there are a lot of points not lying on the graph, you can better draw some more points from the table, to have a preciser idea of the graph.

    so you shouldn't ignore all the numbers in the table, but if there are some who lie a little bit away from the graph, that's fine (when you just have to make a simple graph of a function)

    If there are some things you still don't get, please ask again :-D
    + Don't walk where the path may lead, walk instead where there is no path, and leave a trail...+
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