Table view of the Derivative
We have looked at the derivative function from a graphical point of view.
Let's now look at approximating the derivative function using a table of
values.
1. A parabola
The applet shows a table that represents selected values of a function.
The first row shows a selection of x values, while the second row
shows the corresponding values for f (x). The third row
shows estimated values for the derivative. These are computed from the
pair of x values and the pair of y = f (x)
values above each estimate from the difference quotient
Note
that this is only an estimate for the derivative, as this is calculating
the average rate of change on the interval, not the instantaneous rate of
change. But, since we only have selected values for x and f (x),
that's the best we can do just using the data in the table.
For example, the first derivative estimate is computed as
and the next value is
Can you calculate some of the other values for the
estimated derivative, using the data in the table?
2. Parabola with wider intervals
Select the second example from the drop down menu. This is the same
function, but now the x intervals are farther apart. The
derivative is still estimated using the difference quotient, but in this
example the denominator is 2 instead of 1.
3. A linear function
Select the third example, a linear function. Compute one or two
derivative estimates and check that your calculations match those in the
table. What do you notice about the derivative?
4. A constant function
Select the fourth example, a constant function. Why is the derivative
always 0?
5. An exponential function
Select the fifth example, an exponential function. Does there seem to
be some relationship between the derivative and the value of the
function? We will return to this in the future.
6. A hyperbola
Select the sixth example, a hyperbola. Why are the derivative estimates
negative?
7. A sine curve
Select the seventh example, a sine curve. Does it make sense for the values of the derivative to change around like they seem to do? Is there an upper and lower bound on the values of the derivative function?
Explore
You can make your own example by typing a function definition into the
"f(x)=" box. You can also select the starting x value and the step
size between x values.
While you are here..
... I have a small favor to ask. Over the years we have used advertising to support the site so it can remain free for everyone.
However, advertising revenue is falling and I have always hated the ads. So, would you go to Patreon and become a patron of the site?
When we reach the goal I will remove all advertising from the site.
It only takes a minute and any amount would be greatly appreciated.
Thank you for considering it! – John Page
Become a patron of the site at patreon.com/mathopenref
Other differentiation topics
Acknowledgements
Derived from the work of Thomas S. Downey under a Creative Commons Attribution 3.0 License.
