## Presentation on theme: "4.3 exactly how Derivatives influence the shape of a Graph"— Presentation transcript:

1 4.3 just how Derivatives impact the form of a GraphAPPLICATIONS the DIFFERENTIATION. 4.3 how Derivatives affect the shape of a Graph In this section, we will learn: just how the derivative of a role gives us the direction in i m sorry the curve proceeds at every point.

2 WHAT go f’ SAY about f ? to see how the derivative the f deserve to tell united state where a role is enhancing or decreasing, look at the figure. Raising functions and also decreasing features were characterized in section 1.1

3 WHAT does f’ SAY about f ? in between A and B and between C and D, the tangent lines have actually positive slope. So, f "(x) > 0. Between B and C, The tangent lines Have negative slope. So, f "(x)

0. In between B and C, The tangent lines. Have an adverse slope. So, f (x)

4 INCREASING/DECREASING check (I/D TEST)If f "(x) > 0 on an interval, climate f is boosting on that interval. If f "(x)

0 on one interval, climate f is enhancing on the interval. If f (x)

5 I/D TEST instance 1 uncover where the role f(x) = 3x4 – 4x3 – 12x is increasing and also where that is decreasing.

6 f "(x) = 12x3 - 12x2 - 24x = 12x(x – 2)(x + 1)I/D TEST instance 1 f "(x) = 12x3 - 12x2 - 24x = 12x(x – 2)(x + 1) To use the identifier Test, we have to know wherein f "(x) > 0 and also where f "(x) This relies on the indications of the three determinants of f "(x)—namely, 12x, x – 2, and also x + 1.

0 and also where f (x)

7 I/D TEST instance 1 We divide the actual line into intervals who endpoints room the critical numbers -1, 0, and also 2 and also arrange our occupational in a chart. F "(x) = 12x(x – 2)(x + 1)

8 WHAT go f " SAY about f ? recall from section 4.1 that, if f has a local maximum or minimum in ~ c, climate c must be a an essential number that f (by Fermat’s Theorem). However, not every crucial number gives rise come a maximum or a minimum. So, we need a check that will certainly tell united state whether or no f has actually a regional maximum or minimum at a vital number.

9 WHAT walk f’ SAY around f ? You deserve to see from the figure that f(0) = 5 is a regional maximum worth of f because f increases on (-1, 0) and decreases on (0, 2). In regards to derivatives, f "(x) > 0 for -1 f "(x)

0 for -1

10 Suppose that c is a an important number the a consistent function f.

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FIRST DERIVATIVE TEST expect that c is a crucial number of a continuous function f. If f " alters from hopeful to an adverse at c, then f has actually a regional maximum at c.

11 b. If f’ transforms from an adverse to positive at c, climate f has actually a localFIRST DERIVATIVE check b. If f’ changes from an unfavorable to positive at c, climate f has actually a local minimum at c.

12 c. If f " walk not readjust sign in ~ c—for example, FIRST DERIVATIVE check c. If f " does not readjust sign in ~ c—for example, if f " is positive on both political parties of c or an adverse on both sides—then f has no neighborhood maximum or minimum at c.

13 WHAT walk f’ SAY around f ? example 2 discover the local minimum and maximum values of the role f in example 1.

14 WHAT go f’ SAY around f ? example 2 indigenous the graph in the solution to example 1, we check out that f "(x) transforms from an unfavorable to positive at -1. So, f(-1) = 0 is a neighborhood minimum worth by the an initial Derivative Test.

15 Similarly, f " transforms from an adverse to confident at 2.WHAT walk f’ SAY around f ? example 2 Similarly, f " transforms from an adverse to optimistic at 2. So, f(2) = -27 is also a local minimum value.

16 WHAT does f’ SAY around f ? example 2 As formerly noted, f(0) = 5 is a regional maximum value due to the fact that f "(x) transforms from optimistic to an adverse at 0.

17 Find the local maximum and minimum values of the functionWHAT walk f’ SAY around f ? example 3 find the neighborhood maximum and also minimum values of the role g(x) = x + 2 sin x 0 ≤ x ≤ 2π

18 To find the vital numbers the g, we differentiate:WHAT walk f’ SAY around f ? instance 3 To uncover the an essential numbers that g, us differentiate: g"(x) = cos x So, g’(x) = 0 when cos x = - ½. The options of this equation space 2π/3 and 4π/3.

19 So, we analysis g in the following table.WHAT walk f’ SAY around f ? example 3 together g is differentiable everywhere, the only an essential numbers room 2π/3 and 4π/3. So, we analyze g in the complying with table.

20 WHAT walk f’ SAY about f ? example 3 as g"(x) transforms from confident to an adverse at 2π/3, the very first Derivative check tells united state that there is a regional maximum in ~ 2π/3. The regional maximum worth is:

21 Likewise, g"(x) changes from negative to positive at 4π/3.WHAT go f’ SAY around f ? example 3 Likewise, g"(x) changes from an adverse to optimistic at 4π/3. So, a local minimum worth is:

22 The graph the g supports our conclusion.WHAT go f’ SAY about f ? example 3 The graph the g support our conclusion.

23 The figure shows the graphs of 2 increasing functions on (a, b).WHAT go f "" SAY around f ? The figure shows the graphs of two increasing attributes on (a, b).

24 WHAT does f’’ SAY about f ?Both graphs join allude A to suggest B, however they watch different due to the fact that they bending in various directions. How can we distinguish between these two species of behavior?

25 WHAT does f’’ SAY around f ?Here, tangents to this curves have been attracted at number of points.

26 CONCAVITY—DEFINITIONIf the graph that f lies above all of its tangents on one interval I, that is referred to as concave upward on I. If the graph of f lies below all of its tangents ~ above I, the is called concave downward on I.

27 CONCAVITY The number shows the graph that a role that is concave upward (CU) on the intervals (b, c), (d, e), and also (e, p) and concave downward (CD) ~ above the intervals (a, b), (c, d), and (p, q).

28 CONCAVITY native this figure, you deserve to see that, going from left to right, the slope of the tangent increases. This means that the derivative f " is an increasing duty and thus its derivative f "" is positive.

29 So, f " decreases and also therefore f "" is negative.CONCAVITY Likewise, in this figure, the slope of the tangent decreases from left to right. So, f " decreases and also therefore f "" is negative. This reasoning have the right to be reversed and suggests the the following theorem is true.

30 CONCAVITY test – 2nd DERIVATIVE TESTIf f ""(x) > 0 for every x in I, climate the graph that f is concave upward (MIN) top top I. If f ""(x)

0 for all x in I, then the graph the f is concave upward (MIN) ~ above I. If f (x)

31 B, C, D, and P room points the inflection.

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INFLECTION point B, C, D, and also P are points of inflection.

32 INFLECTION allude In check out of the Concavity Test, there is a allude of inflammation at any point where the second derivative alters sign.

33 SECOND DERIVATIVE TESTSuppose f "" is continuous near c. If f "(c) = 0 and also f ""(c) > 0, then f has actually a regional minimum at c. B. If f "(c) = 0 and f ""(c) maximum in ~ c.

0, climate f has a local. Minimum in ~ c. B. If f (c) = 0 and also f (c)

34 WHAT does f’’ SAY around f ?Example 6 talk about the curve y = x4 – 4x3 v respect to concavity, point out of inflection, and local maxima and minima. Use this information to sketch the curve.

35 WHAT does f’’ SAY about f ?Example 6 If f(x) = x4 – 4x3, then: f "(x) = 4x3 – 12x2 = 4x2(x – 3) f ""(x) = 12x2 – 24x = 12x(x – 2)

36 WHAT go f’’ SAY around f ?Example 6 To uncover the critical numbers, we set f "(x) = 4x2(x – 3)= 0 and obtain x = 0 and also x = 3. To use the 2nd Derivative Test, us evaluate f "" in ~ these vital numbers: f ""(0) = f ""(3) = 36 > 0 Note: f ""(x) = 12x(x – 2)

0. Note: f (x) = 12x(x – 2)">

37 WHAT does f’’ SAY around f ?Example 6 f ""(3) > 0 suggests f(3) = -27 is a neighborhood minimum. Since f ""(0) = 0, the second Derivative Test offers no information around the critical number 0.

0 means f(3) = -27 is a local minimum. Due to the fact that f (0) = 0, the 2nd Derivative Test gives no information about the vital number 0.">

38 WHAT does f’’ SAY around f ?Example 6 However, since f "(x)

39 WHAT does f’’ SAY around f ?Example 6 because that f ""(x) = 0 we have f ""(-1) > 0 and f ""(1) The suggest (0, 0) is an inflection point—since the curve alters from concave increase to concave bottom there. Note: f ""(x) = 12x(x – 2)

0 and also f (1)

40 WHAT go f’’ SAY around f ?Example 6 for f ""(2) = 0 we have f ""(1) 0. Hence, (2, -16) is an inflammation point—since the curve changes from concave downward to concave increase there. Note: f ""(x) = 12x(x – 2)

41 WHAT walk f’’ SAY around f ?Example 6 utilizing the regional minimum, the intervals that concavity, and also the inflammation points, we sketch the curve.

42 The 2nd Derivative check is inconclusive once f ""(c) = 0.NOTE The 2nd Derivative test is inconclusive once f ""(c) = 0. In other words, at such a point, there can be a maximum, a minimum, or no (as in the example). The test also fails once f ""(c) does not exist. In such cases, the very first Derivative Test have to be used.