- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals3h 25m
4. Applications of Derivatives
Differentials
Problem 4.7.53
Textbook Question
17–83. Limits Evaluate the following limits. Use l’Hôpital’s Rule when it is convenient and applicable.
lim_x→0 x csc x

1
First, recognize that the limit \( \lim_{x \to 0} x \csc x \) can be rewritten using the identity \( \csc x = \frac{1}{\sin x} \). Thus, the expression becomes \( \lim_{x \to 0} \frac{x}{\sin x} \).
Observe that as \( x \to 0 \), both the numerator and the denominator approach 0, creating an indeterminate form \( \frac{0}{0} \). This is a situation where l'Hôpital's Rule can be applied.
Apply l'Hôpital's Rule, which states that if \( \lim_{x \to a} \frac{f(x)}{g(x)} \) results in an indeterminate form \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \), then \( \lim_{x \to a} \frac{f(x)}{g(x)} = \lim_{x \to a} \frac{f'(x)}{g'(x)} \), provided the limit on the right exists.
Differentiate the numerator and the denominator separately: the derivative of \( x \) is \( 1 \), and the derivative of \( \sin x \) is \( \cos x \).
Now, evaluate the new limit: \( \lim_{x \to 0} \frac{1}{\cos x} \). Since \( \cos 0 = 1 \), the limit simplifies to \( \frac{1}{1} \).
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