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Math Help - Graphing Derivatives

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    Graphing Derivatives

    I am confused how to graph derivatives. I attached an image with the graph of a function and then I tried to graph the derivative. The part that gets me confused is figuring out the slope of the derivative. I know this is an approximation, but sometimes I see the graph of a function having a positive slope, and then the derivative has a negative slope. My teacher says to look at it like taking a limit from one side. Example, if a function approaches an undefined slope (like a cusps or a corner), then take the limit from both sides, so if the function approaches the cusp positively from the left the derivative is approaching negatively from the left. I guess it's just this reversal of perception that's confusing me at the moment.

    Can someone check out my attached graphs and let me know if the derivates are correct? The graph on the left is the function(x) and the one in dark black on the right is f'(x). Thanks.
    Attached Thumbnails Attached Thumbnails Graphing Derivatives-graphing-derivative-1-.jpg   Graphing Derivatives-graphing-derivative-3-.jpg  
    Last edited by AZach; September 22nd 2012 at 08:56 AM.
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Graphing Derivatives

    Yes, that sketch looks good.
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    Re: Graphing Derivatives

    Does it really just help to memorize common functions like square root and reciprocal and knowing how the derivates will look? I added another graph with a semi circle too.
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    MHF Contributor MarkFL's Avatar
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    Re: Graphing Derivatives

    For your second sketch, you need to reflect about the x-axis. The slope of the semi-circle is positive on the left of the y-axis and negative on the right.

    As far as memorization, I have always tried to keep that to a minimum.
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    Re: Graphing Derivatives

    Ohh I think I get it know. I wasn't connecting the fact that a positive slope is above the x axis and negative is below.. . . ...
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