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Discovering Differentiability

Answer the three background questions first, then explore the applet. The checkboxes in the applet below will show you five different functions. Each function has at least one point at which it is not differentiable. Examine the functions one by one and determine the point(s) at which they are not differentiable. There is a hint if you need it. Answer the questions that follow the applet as you go.

1.

For to exist, which of the following must be true?

Select all that apply
  • A
  • B
  • C
  • D
  • E
Check my answer (3)

2.

Can a function be discontinuous at a point if the limit is defined at that point?

3.

For a function to be differentiable at a point x=a, the value of the derivative must exist there. How do we define the derivative of a function at a point?

4.

At what x-value (approximately) is the derivative of the function in Example 1 undefined? Why?

5.

If the limit exists at a hole on a function, how come the derivative doesn't?

6.

At what x-value is the derivative of the function in Example 2 undefined? Why?

7.

At the "vertex" of the graph in Example 3, we essentially have two lines meeting. Estimate the slope of the line to the right of the vertex. Estimate the slope of the line to the left of the vertex.

8.

At what x-value (approximately) is the derivative of the function in Example 3 undefined? Why?

9.

Can a function be continuous everywhere but not differentiable everywhere?

Select all that apply
  • A
  • B
Check my answer (3)

10.

What happens to the slope of the graph in Example 4 as you approach the minimum point from either direction?

11.

At what x-value (approximately) is the derivative of the function in Example 4 undefined? Why?

12.

Why is the slope of a vertical line undefined?

13.

At what x-value (approximately) is the derivative of the function in Example 5 undefined? Why?

14.

What are the different characteristics of a graph that will show you that it is not differentiable at that point?