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Math Help - Understanding concepts

  1. #1
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    Understanding concepts

    URGENT HELP!! PLEASE! PLEASE! PLEASE! answer this ;(


    What is log x?
    What is log y?

    for y=ax^n why is it appropriate to plot: log x vs log y?
    for y=Ae^kx why is appropriate to plot: x vs log y?

    ambient room temp:25
    e.g data
    time x=0,2,4,6,8,10....
    temp y=76,72,64,59,55,52...
    difference of temp from ambient temp: 51,47 39,34,30,27 ...

    Can anyone explain simply?
    please anyone help I really need to understand this (it means alot as this is the end of school year)
    Any help would be greatly appreciated

    Maths help 246
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  2. #2
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    Re: Understanding concepts

    Hey Mathshelp246.

    Taking logs of both sides shows how something change exponentially.

    If something is exponentially increasing then a log plot will show a straight line with a positive gradient. If it is exponentially decreasing, then it will be a straight line with a negative gradient.

    If something is sub-exponential then the line will be very flat and usually have some kind of asymptote (like a horizontal one).
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  3. #3
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    Re: Understanding concepts

    Ohh I think I might be getting what you mean!?

    why you take log x vs log y - it is a straight line (linear) it is showing how both x and y change exponentially- both are the same (a log of each x and y was taken)
    Where as when it is x vs Log y - is at every x value, there is a exponential change in y (i.e. log y)- eventually y will level off, therefore the curve will have an asymptote line for the varible temp (y)

    Is this what you mean?

    ** also if its not too much trouble is: log y the "difference of temperature from ambient room temperature"?**
    Thank you so much
    means alot ...^_^...
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  4. #4
    MHF Contributor
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    Re: Understanding concepts

    Basically what I mean is that the slope of the line tells you how its changing on a log scale.

    If its a positive slope its changing exponentially in a linear fashion. If its close to flat though it means its changing in a polynomial manner (or sub exponential way).
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