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2.6: Summary

  • Page ID
    121091
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    1. Graphs of time-dependent data are helpful to visualize trends such as increasing and decreasing values, steepness, linearity, and so on.
    2. An average rate of change is the ratio of change in a dependent variable \((y)\) over a range of the independent variable \((x)\), often denoted \(\Delta y / \Delta x\).
    3. A secant line is a straight line through any two points on the graph of a function. The slope of a secant line is the average rate of change of the function over interval between the \(x\) coordinates of the two points.
    4. The average rate of change of a function \(y=f(x)\) on \(x_{0} \leq x \leq x_{0}+h\) can be computed by the ratio

    \[\frac{\Delta y}{\Delta x}=\frac{\text { Change in } y}{\text { Change in } x}=\frac{\left[f\left(x_{0}+h\right)-f\left(x_{0}\right)\right]}{h} \nonumber \]

    1. The instantaneous rate of change of a function \(f(x)\) at \(x_{0}\) can be found by taking the limit as \(h \rightarrow 0\) of the average rate of change on \(x_{0} \leq x \leq x_{0}+h\).
    2. The derivative of a function \(y=f(x)\) at a point \(x_{0}\) is the same as the instantaneous rate of change of \(f\) at \(x_{0}\).
    3. In the case of time-dependent data, refining the data can lead to a better and better approximation of instantaneous rates of change.
    4. This chapter explored data related to the following time-dependent processes: (a) height of a falling object; (b) temperature of heating/cooling milk; and (c) swimming velocity of Bluefin tuna.
    Quick Concept Checks
    1. How do we calculate average rate of change of a time dependent process over a given interval?
    2. Over what interval does the function depicted in the graph below have the greatest average rate of change? Smallest average rate of change?
    3. Given the function defined by \(\{(1,3),(2,5),(3,7)\}\), how many different secant lines can be formed?
    4. Use the definition to calculate the derivative of \(f(x)=4 x^{2}+3\) at \(x_{0}=1\).

    This page titled 2.6: Summary is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Leah Edelstein-Keshet via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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