Let f (x) = x2 cos 1 x , x _= 0 (a) Use a graphing calculator to sketch the graph of y = f (x). (b) Show that x2 x2 cos 1 x x2 holds for x _= 0 . (c) Use your result in (b) and the sandwich theorem to show that lim x0 x2 cos 1 x = 0
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Textbook Solutions for Calculus For Biology and Medicine (Calculus for Life Sciences Series)
Question
(a) Use a graphing calculator to sketch the graph of f (x) = eax sin x, x 0 for a = 0.1, 0.01, 0, 0.01, and 0.1. (b) Which part of the function f (x) produces the oscillations that you see in the graphs sketched in (a)? (c) Describe in words the effect that the value of a has on the shape of the graph of f (x). (d) Graph f (x) = eax sin x, g(x) = eax , and h(x) = eax together in one coordinate system for (i) a = 0.1 and (ii) a = 0.1. [Use separate coordinate systems for (i) and (ii).] Explain what you see in each case. Show that eax eax sin x eax Use this pair of inequalities to determine the values of a for which lim x f (x) exists, and find the limiting value.
Solution
The first step in solving 3.4 problem number 21 trying to solve the problem we have to refer to the textbook question: (a) Use a graphing calculator to sketch the graph of f (x) = eax sin x, x 0 for a = 0.1, 0.01, 0, 0.01, and 0.1. (b) Which part of the function f (x) produces the oscillations that you see in the graphs sketched in (a)? (c) Describe in words the effect that the value of a has on the shape of the graph of f (x). (d) Graph f (x) = eax sin x, g(x) = eax , and h(x) = eax together in one coordinate system for (i) a = 0.1 and (ii) a = 0.1. [Use separate coordinate systems for (i) and (ii).] Explain what you see in each case. Show that eax eax sin x eax Use this pair of inequalities to determine the values of a for which lim x f (x) exists, and find the limiting value.
From the textbook chapter The Sandwich Theorem and Some Trigonometric Limits you will find a few key concepts needed to solve this.
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