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5) Use the Squeeze Theorem to show that \( \lim _{x \rightarrow 0} x \sin \frac{1}{x}=0 \)

Ask by Murray Marshall. in the United States
Feb 26,2025

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Answer

To show that \( \lim_{x \to 0} x \sin\left(\frac{1}{x}\right) = 0 \) using the Squeeze Theorem: 1. Since \( -1 \leq \sin\left(\frac{1}{x}\right) \leq 1 \) for all \( x \neq 0 \), 2. Multiply by \( x \): \( -|x| \leq x \sin\left(\frac{1}{x}\right) \leq |x| \). 3. Taking the limit as \( x \to 0 \), both \( -|x| \) and \( |x| \) approach 0. 4. By the Squeeze Theorem, \( x \sin\left(\frac{1}{x}\right) \) also approaches 0. Therefore, \( \lim_{x \to 0} x \sin\left(\frac{1}{x}\right) = 0 \).

Solution

To show that limₓ→0 x sin(1/x) = 0 using the Squeeze Theorem, follow these steps: 1. Note that for all real numbers t, we have –1 ≤ sin(t) ≤ 1. With t = 1/x, it follows that   –1 ≤ sin(1/x) ≤ 1  (for all x ≠ 0). 2. Multiply the inequality by x. Since we need to be careful about the sign of x, consider the absolute value:   |x sin(1/x)| ≤ |x|. 3. So we have   –|x| ≤ x sin(1/x) ≤ |x|. 4. Now, take the limit as x approaches 0 in the inequality. Since limₓ→0 (–|x|) = 0 and limₓ→0 |x| = 0, by the Squeeze Theorem, we conclude that   limₓ→0 x sin(1/x) = 0. Thus, the limit is 0.

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To show that \( \lim_{x \rightarrow 0} x \sin \frac{1}{x} = 0 \) using the Squeeze Theorem, we start with the fact that the sine function is bounded between -1 and 1. This gives us the inequality: \[ -1 \leq \sin \frac{1}{x} \leq 1 \] Multiplying all parts of this inequality by \( x \) (taking care that \( x \) is approaching 0, where we can consider both positive and negative cases), we get: \[ -x \leq x \sin \frac{1}{x} \leq x \quad \text{for } x > 0 \] \[ x \leq x \sin \frac{1}{x} \leq -x \quad \text{for } x < 0 \] Now, we can rewrite this as two inequalities for \( x \) approaching 0: \[ -x \leq x \sin \frac{1}{x} \leq x \] Next, as \( x \) approaches 0, both bounds \( -x \) and \( x \) approach 0. Using the Squeeze Theorem, since \( x \sin \frac{1}{x} \) is squeezed between two expressions that both converge to 0, we conclude: \[ \lim_{x \rightarrow 0} x \sin \frac{1}{x} = 0 \] Thus, we have used the Squeeze Theorem to establish our result!

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