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  1. AP Calculus
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What does the graph of xcos⁡(1x)x\cos(\frac{1}{x})xcos(x1​) squeezed between −∣x∣-|x|−∣x∣ and ∣x∣|x|∣x∣ tell us?

It visually confirms that as xxx approaches 0, xcos⁡(1x)x\cos(\frac{1}{x})xcos(x1​) is forced to approach 0 as well.

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What does the graph of xcos⁡(1x)x\cos(\frac{1}{x})xcos(x1​) squeezed between −∣x∣-|x|−∣x∣ and ∣x∣|x|∣x∣ tell us?

It visually confirms that as xxx approaches 0, xcos⁡(1x)x\cos(\frac{1}{x})xcos(x1​) is forced to approach 0 as well.

Steps to apply the Squeeze Theorem.

  1. Identify the function. 2. Find bounding functions. 3. Show bounding functions have the same limit. 4. Conclude the limit of the original function.

How to find the lim⁡x→0xcos⁡(1x)\lim_{x \to 0} x\cos(\frac{1}{x})limx→0​xcos(x1​) using the Squeeze Theorem.

  1. Recognize −1≤cos⁡(1x)≤1-1 \leq \cos(\frac{1}{x}) \leq 1−1≤cos(x1​)≤1. 2. Multiply by xxx: −∣x∣≤xcos⁡(1x)≤∣x∣-|x| \leq x\cos(\frac{1}{x}) \leq |x|−∣x∣≤xcos(x1​)≤∣x∣. 3. lim⁡x→0−∣x∣=0\lim_{x \to 0} -|x| = 0limx→0​−∣x∣=0 and lim⁡x→0∣x∣=0\lim_{x \to 0} |x| = 0limx→0​∣x∣=0. 4. Therefore, lim⁡x→0xcos⁡(1x)=0\lim_{x \to 0} x\cos(\frac{1}{x}) = 0limx→0​xcos(x1​)=0.

How do you handle the sign of x when multiplying inequalities?

Use absolute values to ensure inequalities hold for both positive and negative x values.

How to apply the Squeeze Theorem when given g(x)≤k(x)≤h(x)g(x) \leq k(x) \leq h(x)g(x)≤k(x)≤h(x)?

  1. Find lim⁡x→ag(x)\lim_{x \to a} g(x)limx→a​g(x) and lim⁡x→ah(x)\lim_{x \to a} h(x)limx→a​h(x). 2. If both limits are equal to LLL, then lim⁡x→ak(x)=L\lim_{x \to a} k(x) = Llimx→a​k(x)=L.

State the Squeeze Theorem.

If f(x)≤g(x)≤h(x)f(x) \leq g(x) \leq h(x)f(x)≤g(x)≤h(x) for all xxx in an interval containing aaa (except possibly at aaa itself) and lim⁡x→af(x)=lim⁡x→ah(x)=L\lim_{x \to a} f(x) = \lim_{x \to a} h(x) = Llimx→a​f(x)=limx→a​h(x)=L, then lim⁡x→ag(x)=L\lim_{x \to a} g(x) = Llimx→a​g(x)=L.