Homework # 8 - Math 149
The problems on this homework must be done alone. The honor code is in effect.
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Evaluate the following limits.
1. While it's true that $$\lim_{x \rightarrow 0} \frac{\sin 2x}{3x} = \frac{2}{3},$$ what's wrong with the following "proof"? $$\begin{array}{ll} & \lim_{x \rightarrow 0} \frac{\sin 2x}{3x} \\ = & \lim_{x \rightarrow 0} \frac{2\sin x}{3x} \\ = & \lim_{x \rightarrow 0} \frac{2}{3} \frac{\sin x}{x} \\ = & \frac{2}{3}\lim_{x \rightarrow 0} \frac{\sin x}{x} \\ = & \frac{2}{3} (1) \\ = & \frac{2}{3}\end{array}$$
a. \(\sin 2x \neq 2\sin x\)
b. You can't move the \(\frac{2}{3}\) from inside the limit to outside.
c. \(\lim_{x\rightarrow 0} \frac{\sin x}{x} \neq 1\)
c. Nothing is wrong here.
2. Consider the graph in section 1.4 question 4. At \( x = -2 \)
a. the function has a removable discontinuity.
b. the function has a jump discontinuity.
c. the function has an infinite discontinuity
d. the function has an oscillatory discontinuity.
e. the function does not have a discontinuity.
3. Consider the graph in section 1.4 question 6. At \( x = -1 \)
4. If we wanted to use the squeeze theorem to show that the limit $$\lim_{x \rightarrow 0} x \sin(\frac{1}{x}) = 0,$$ we could sandwich the function \(f(x) = x \sin(\frac{1}{x})\) between which two functions?
a. \(h(x) = -x^2\) and \(g(x) = x^2\)
b. \(h(x) = -\mid x \mid\) and \(g(x) = \mid x \mid\)
c. \(h(x) = -x^3\) and \(g(x) = x^3\)
d. \(h(x) = -x^4\) and \(g(x) = x^4\)