Math Problem Statement

Evaluate the following limit using L'Hospital's rule where appropriate: lim(x → 0) [sin(10x) / tan(4x)]

Solution

To solve the given limit using L'Hospital's Rule, we must first evaluate if the limit results in an indeterminate form like 00\frac{0}{0}. The limit is:

limx0sin(10x)tan(4x)\lim_{x \to 0} \frac{\sin(10x)}{\tan(4x)}

Step 1: Check for indeterminate form

As x0x \to 0:

  • sin(10x)sin(0)=0\sin(10x) \to \sin(0) = 0
  • tan(4x)tan(0)=0\tan(4x) \to \tan(0) = 0

Thus, the limit is of the form 00\frac{0}{0}, so we can apply L'Hospital's Rule, which states that if the limit results in 00\frac{0}{0}, we take the derivative of the numerator and denominator separately.

Step 2: Differentiate the numerator and denominator

  • The derivative of sin(10x)\sin(10x) is 10cos(10x)10\cos(10x).
  • The derivative of tan(4x)\tan(4x) is 4sec2(4x)4\sec^2(4x).

Thus, the new limit becomes:

limx010cos(10x)4sec2(4x)\lim_{x \to 0} \frac{10\cos(10x)}{4\sec^2(4x)}

Step 3: Simplify the expression

At x=0x = 0:

  • cos(10x)cos(0)=1\cos(10x) \to \cos(0) = 1
  • sec(4x)=1cos(4x)\sec(4x) = \frac{1}{\cos(4x)}, and cos(4x)cos(0)=1\cos(4x) \to \cos(0) = 1, so sec2(4x)1\sec^2(4x) \to 1

Therefore, the limit simplifies to:

limx010141=104=52\lim_{x \to 0} \frac{10 \cdot 1}{4 \cdot 1} = \frac{10}{4} = \frac{5}{2}

Final Answer:

limx0sin(10x)tan(4x)=52\lim_{x \to 0} \frac{\sin(10x)}{\tan(4x)} = \frac{5}{2}

Would you like more details or have any questions about the steps?

Here are five related questions:

  1. How is L'Hospital's Rule applied when dealing with indeterminate forms?
  2. What are the common indeterminate forms where L'Hospital's Rule can be applied?
  3. How do you differentiate trigonometric functions like sin(x)\sin(x) and tan(x)\tan(x)?
  4. What happens if the limit still results in an indeterminate form after applying L'Hospital's Rule once?
  5. Can L'Hospital's Rule be applied to limits involving infinity?

Tip: Always check if the original limit results in an indeterminate form before applying L'Hospital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
L'Hospital's Rule
Trigonometry

Formulas

L'Hospital's Rule: lim(x → c) [f(x)/g(x)] = lim(x → c) [f'(x)/g'(x)] if the original form is 0/0 or ∞/∞
Derivative of sin(x): d/dx[sin(kx)] = kcos(kx)
Derivative of tan(x): d/dx[tan(kx)] = ksec^2(kx)

Theorems

L'Hospital's Rule

Suitable Grade Level

College/University Level Calculus