Funky Functions
Homework
Math 555


To find some funky functions:
Examples of Continuous and Differentiable Functions
Example 1: A function that is not continuous at any point in R.
Example 2: A function that is continuous at the irrational numbers and discontinuous at the rational numbers.
Example 3: A function that is differentiable, but the derivative is not continuous.
Example 4: A function that is n-times differentiable, but not (n+1)-times differentiable.
Example 5: A function that is not zero, infinitely often differentiable, but the n-th derivative at zero is always zero.
Example 6: A function that is continuous everywhere and nowhere differentiable in R.
Example 7: A continuous, non-constant, differentiable function whose derivative is zero everywhere except on a set of length Lebesgue measure zero.

Below are some comments on the functions. Several of you said the you could not view the "plugin"'s for the above examples. So I have tried to work around this problem. The plugin's are now working on the computer in my office. You are welcome to stop by my office and view them. I have made some plots using Maple; the Maple worksheets and HTML files of the excuted Maple worksheets are below. Maple is on most of the computers around LeConte. The actual Maple Worksheet has the advantage that you can adjust the code to see what you are interested in.
Example 1 No plugins. This is Exmple 4.2.2c from our textbook (Stoll, 2nd edition).

Example 2 No plugins. This is Exmple 4.2.2g from our textbook.

Example 3 Plugins. See homework problem 5.1.13.

Example 4 Plugins.

Example 5 Plugins. Example 6 Plugins. Example 8.5.3 in our textbook. A Weierstrass Function is a function of the form
Σ n=0 &infin   an cos (bn π x)           or           Σ n=0 &infin   an sin (bn π x)
where there are some kind of restriction on a and b.

Example 7 No Plugins but also no graphics. The example is the Cantor Function, which we have talked about in class. It is a particular case of a devil's staircase.


Findable from URL: http://people.math.sc.edu/girardi/