Chapter 3

41. The figure shows the graphs of three functions. One is the
position function of a car, one is the velocity of the car, and
one is its acceleration. Identify each curve, and explain your
choices.
(b) Show thatf'(O) does not exist.
(c) Show that y =$ has a vertical tangent line at (0, 0).
(Recall the shape of the graph of f. See Figure 13 in Section
1.2.)
48. (a) If g(x) = X 2 3 / , show that g'(O) does not exist.
(b) If a¥- 0, find g'(a).
(c) Show that y = X 2 / 3 has a vertical tangent line at (0, 0).
~ (d) Illustrate part (c) by graphing y = X 2 / 3 •
lID Show that the function f(x) = I x - 61 is not differentiable
at 6. Find a formula for I' and sketch its graph.
42. The figure shows the graphs of four functions. One is the
position function of a car, one is the velocity of the car, one is
its acceleration, and one is its jerk. Identify each curve, and
explain your choices.
50. Where is the greatest integer function f(x) = [x ~ not differentiable?
Find a formula for I' and sketch its graph.
[!.J (a) Sketch the graph of the function f(x) = x Ix I·
(b) For what values of x is f differentiable?
(c) Find a formula for 1'.
52. The left-hand and right-hand derivatives of f at a are
defined by
f'-(a) = Jim f(a + h) - f(a)
h~O- h
f
' ( ) I' f(a + h) - f(a)
+ a - 1m
h~O+ h
~ 43-44 Use the definition of a derivative to findf'(x) and rCx).
Then graph f, 1', and r on a common screen and check to see if
your answers are reasonable.
~~ If f(x) = 2x 2 - x 3 , findf'(x), r(x),flll(x), and f(4)(X).
Graph f, 1', f", and fill on a common screen. Are the
graphs consistent with the geometric interpretations of these
derivatives?
46. (a) The graph of a position function of a car is shown, where
s is measured in meters and t in seconds. Use it to graph
the velocity and acceleration of the car. What is the acceleration
at t = 10 seconds?
(b) Use the acceleration curve from part (a) to estimate the
jerk at t = 10 seconds. What are the units for jerk?
47. Letf(x) = $.
(a) If a ¥- 0, use Equation
3.1.5 to find f'(a).
if these limits exist. Then f'(a) exists if and only if these onesided
derivatives exist and are equal.
(a) Find f'-(4) andf~(4) for the function
f(x)
0
5-x
= _I_
1
s-x
(b) Sketch the graph of f.
(c) Where is f discontinuous?
(d) Where is f not differentiable?
if x ~ 0
if 0 < x < 4
53. Recall that a function f is called even if f( -x) = f(x) for all
x in its domain and odd if f( -x) = -f(x) for all such x.
Prove each of the following.
(a) The derivative of an even function is an odd function.
(b) The derivative of an odd function is an even function.
54. When you turn on a hot-water faucet, the temperature T of
the water depends on how long the water has been running.
(a) Sketch a possible graph of T as a function of the time t
that has elapsed since the faucet was turned on.
(b) Describe how the rate of change of T with respect to t
varies as t increases.
(c) Sketch a graph of the derivative of T.
55. Let e be the tangent line to the parabola y = x 2 at the point
(I, I). The angle of inclination of e is the angle 4> that e
makes with the positive direction of the x-axis. Calculate 4>
correct to the nearest degree.