1. Calculus I (MAT 145) Dr. Day Wednesday Nov 1, 2017
Using Derivatives: Function Characteristics & Applications (Ch 4)
Determining Function Behavior From its Derivatives (4.3)
Increasing/Decreasing Nature of a Function (first derivative)
Concavity of a Function (second derivative)
Wednesday, November 1, 2017
MAT 145

2. Absolute Extrema—Closed Interval Method
Wednesday, November 1, 2017
MAT 145

3. Absolute and Relative Extremes
Absolute (Global) Extreme: An output of a function such that it is either the greatest (maximum) or the least (minimum) of all possible outputs.
Relative (Local) Extreme: An output of a function such that it is either the greatest (maximum) or the least (minimum) in some small neighborhood along the x-axis.
Extreme Value Theorem: For f(x) continuous on a closed interval, there must be extreme values. If f is continuous on a closed interval [a,b] then f attains an absolute maximum value f(c) and an absolute minimum value f(d) at some numbers c and d in [a,b].
Fermat’s Theorem: If f has a local max or min at x = c and if f ’(c) exists then f ’(c) = 0.
Critical Point: An interior point (not an endpoint) on f(x) with f ’(x) = 0 or f ’(x) undefined. Note: The function MUST EXIST at x = c for a critical point to exist at x = c.
Wednesday, November 1, 2017
MAT 145

4. Relative (Local) Extrema
Where could relative extrema occur?
Critical numbers are the locations where local extrema could occur. Critical points are the points (x- and y-values) that describe both the locations and function values at those points.
Determine critical numbers for
Wednesday, November 1, 2017
MAT 145

5. Fermat’s Theorem
Wednesday, November 1, 2017
MAT 145

6. Absolute Extrema Where and what are the absolute and local extrema?
Wednesday, November 1, 2017
MAT 145

7. Absolute and Relative Extremes
Ways to Find Extrema
Local Extremes: examine behavior at critical points
Absolute Extremes: examine behavior at critical points and at endpoints
Example
Determine critical numbers, absolute extrema, and relative extrema for the unrestricted function (all possible domain values) and then for the restricted domain [−1,3].
Wednesday, November 1, 2017
MAT 145

8. What does f’ tell us about f?
If f’(c)= 0, there is a horizontal tangent to the curve at x=c. This may mean there is a local max or min at x=c.
If f’(c) is undefined, there could be a discontinuity, a vertical tangent, or a cusp (sharp point) at x=c. If f(x) is continuous at x=c, there may be a local max or min at x=c.
Wednesday, November 1, 2017
MAT 145

9. Absolute and Relative Maximums and Minimums
Use the graph of f ’(x) to describe a strategy for identifying the global and local extrema of f, knowing f ’(x). m a t h
Wednesday, November 1, 2017
MAT 145

10. First derivative test
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MAT 145

11. Absolute and Relative Maximums and Minimums
Must every continuous function have critical points on a closed interval? Explain.
Can an increasing function have a local max? Explain.
Wednesday, November 1, 2017
MAT 145

12. Concavity of a Function
Concavity Animations
More Concavity Animations
Wednesday, November 1, 2017
MAT 145

13. Concavity of a Function
Concavity Animations
More Concavity Animations
Wednesday, November 1, 2017
MAT 145

14. What does f’’ tell us about f?
If f’’(c)> 0, then the original curve f(x) is concave up at x=c.
If f’’(c)< 0, then the original curve f(x) is concave down at x=c.
If f’’(c)= 0, then f(x) is neither concave up nor concave down at x=c. And there could be an inflection point on f(x) at x=c.
If f’’(c) is undefined, there could be a discontinuity, a vertical tangent, or a cusp (sharp point) in f’(x) at x=c. There may be a change of concavity in f(x) at x=c.
Wednesday, November 1, 2017
MAT 145

15. Inflection Point
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MAT 145

16. First Derivative Test, Concavity, Second Derivative Test (Sec. 4.3)
Determining Increasing or Decreasing Nature of a Function
If f’(x) > 0, then f is _?_.
If f’(x) < 0, then f is _?_.
Using the First Derivative to Determine Whether an Extreme Value Exists: The First Derivative Test (and first derivative sign charts)
If f’ changes from positive to negative at x=c, then f has a _?_ _?_ at c.
If f’ changes from negative to positive at x=c, then f has a _?_ _?_ at c.
If f’ does not change sign at x=c, then f has neither a local max or min at c.
Concavity of f
If f’’(x) > 0 for all x in some interval I, then the graph is concave up on I.
If f’’(x) < 0 for all x in some interval I, then the graph is concave down on I.
Second derivative Test
If f’(c) = 0 and f’’(c) > 0, then f has a local min at c.
If f’(c) = 0 and f’’(c) < 0, then f has a local max at c.
Wednesday, November 1, 2017
MAT 145

17. Info about f from f ’
Here’s a graph of g’(x). Determine all intervals over which g is increasing and over which g is decreasing. Identify and justify where all local extremes occur.
Wednesday, November 1, 2017
MAT 145

18. Info about f from f ’’
Here’s a graph of h”(x). Determine all intervals over which h is concave up and over which h is concave down. Identify and justify where all points of inflection occur.
Wednesday, November 1, 2017
MAT 145

19. Pulling it all together
For f(x) shown below, use calculus to determine and justify:
All x-axis intervals for which f is increasing
All x-axis intervals for which f is decreasing
The location and value of every local & absolute extreme
All x-axis intervals for which f is concave up
All x-axis intervals for which f is concave down
The location of every point of inflection.
Wednesday, November 1, 2017
MAT 145

20. Wednesday, November 1, 2017
MAT 145

21. Identify Extrema From a Graph
Graph each function. Identify all global and local extremes. For each of those, write a sentence based on this template:
At x = ?, there is a (local/global) (max/min) of y = ?
Wednesday, November 1, 2017
MAT 145

22. Identify Extrema From a Graph
At x = 1 there is a global max of 5. At x = 4 there is a global min of 3.
At x = 0 there is a global max of 4.
There is no global min.
At x = -1 there is a global min of 1/e.
There is no global max.
Wednesday, November 1, 2017
MAT 145

23. Determine the Critical Numbers
For each function, determine every critical number. Unless otherwise restricted, assume that each function’s domain includes all possible values for which that function is defined.
Wednesday, November 1, 2017
MAT 145

24. Determine the Critical Numbers
For each function, determine every critical number. Unless otherwise restricted, assume that each function’s domain includes all possible values for which that function is defined.
Wednesday, November 1, 2017
MAT 145

25. Identify Extrema Using Critical Numbers
For each function, determine every critical number, and then use those critical numbers to determine all absolute extreme values. Note the domain restrictions.
For each extreme value, write a sentence based on this template:
At x = _?_, there is an absolute (max/min) of _?_.
Wednesday, November 1, 2017
MAT 145

26. Identify Extrema Using Critical Numbers
At x = √8 there is a global max of 8. At x = −1 there is a global min of −√15.
At x = −2 there is a global max of 92.
At x = 3 there is a global min of −158.
At x = 1 there is a global max of 1.
At x = 0 there is a global min of 0.
Wednesday, November 1, 2017
MAT 145

27. Absolute and Relative Extremes
Ways to Find Extrema
Local Extremes: Examine behavior at critical points.
Absolute Extremes: Examine behavior at critical points and at endpoints.
Example
Determine critical numbers, absolute extrema, and relative extrema for the unrestricted function (all possible domain values) and then for the restricted domain [−3,1].
Wednesday, November 1, 2017
MAT 145