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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
7장, 문제 7.7.82i

82. Use the definitions of the hyperbolic functions to find each of the following limits.
i. lim(x→-∞) csch x

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Recall the definition of the hyperbolic cosecant function: \(\text{csch}\,x = \frac{1}{\sinh x}\).
Recall the definition of the hyperbolic sine function: \(\sinh x = \frac{e^{x} - e^{-x}}{2}\).
Analyze the behavior of \(\sinh x\) as \(x \to -\infty\). Since \(e^{x} \to 0\) and \(e^{-x} \to \infty\) as \(x \to -\infty\), determine the dominant term in \(\sinh x\).
Use the dominant term to approximate \(\sinh x\) for very large negative \(x\), then find the corresponding behavior of \(\text{csch}\,x = \frac{1}{\sinh x}\).
Conclude the limit \(\lim_{x \to -\infty} \text{csch}\,x\) based on the sign and magnitude of the approximation.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Definition of Hyperbolic Cosecant (csch x)

The hyperbolic cosecant function, csch x, is defined as 1 divided by the hyperbolic sine of x, i.e., csch x = 1/sinh x. Understanding this definition is essential to rewrite the limit expression in terms of exponential functions for easier evaluation.
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Definition of the Definite Integral

Behavior of Exponential Functions as x Approaches Negative Infinity

As x approaches negative infinity, the exponential function e^x approaches zero, while e^{-x} grows without bound. Recognizing this behavior helps simplify expressions involving hyperbolic functions, which are combinations of exponentials, to determine their limits.
추천 영상:
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Graphs of Exponential Functions

Limit Evaluation Using Exponential Definitions

By expressing hyperbolic functions in terms of exponentials, limits can be evaluated by analyzing dominant terms as x approaches infinity or negative infinity. This method allows for straightforward calculation of limits by focusing on the leading exponential behavior.
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Solving Exponential Equations Using Logs