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Ch. 2 - Limits
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 2.3.61

Find the following limits or state that they do not exist. Assume a, b, c, and k are fixed real numbers.


limx01cos(x)cos2(x)3cos(x)+2{\(\displaystyle\]\lim\)_{x\(\to\)0}\(\frac{1-\cos\left(x\right)}{\cos^2\left(x\right)-3\cos\left(x\right)+2}\)}

검증된 단계별 안내
1
Step 1: Recognize that the limit involves a trigonometric expression. The numerator is \(1 - \cos(x)\), which can be approximated using the Taylor series expansion for \(\cos(x)\) around \(x = 0\): \(\cos(x) \approx 1 - \frac{x^2}{2}\). Therefore, \(1 - \cos(x) \approx \frac{x^2}{2}\) for small \(x\).
Step 2: Factor the denominator \(\cos^2(x) - 3\cos(x) + 2\). Notice that this is a quadratic in terms of \(\cos(x)\). Let \(y = \cos(x)\), then the expression becomes \(y^2 - 3y + 2\). Factor this quadratic to get \((y - 1)(y - 2)\). Therefore, \(\cos^2(x) - 3\cos(x) + 2 = (\cos(x) - 1)(\cos(x) - 2)\).
Step 3: Substitute the factored form of the denominator back into the limit expression: \(\lim_{x \to 0} \frac{1 - \cos(x)}{(\cos(x) - 1)(\cos(x) - 2)}\). Notice that \(\cos(x) - 1\) is a common factor in both the numerator and the denominator.
Step 4: Simplify the expression by canceling the common factor \(\cos(x) - 1\) from the numerator and the denominator. This gives \(\lim_{x \to 0} \frac{1}{\cos(x) - 2}\).
Step 5: Evaluate the simplified limit as \(x\) approaches 0. Since \(\cos(0) = 1\), substitute \(x = 0\) into the simplified expression to find the limit.

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주요 개념

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Limits are fundamental in calculus, representing the value that a function approaches as the input approaches a certain point. In this question, we are tasked with finding the limit of a function as x approaches 0. Understanding how to evaluate limits, especially when direct substitution leads to indeterminate forms, is crucial for solving the problem.
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