Math Problem Statement

Find \( \lim_{x \to 0} \frac{\cos(4x) \cdot \tan(4x)}{6x} \).

Solution

The problem you uploaded asks to find the following limit:

limx0cos(4x)tan(4x)6x\lim_{x \to 0} \frac{\cos(4x) \cdot \tan(4x)}{6x}

Step-by-Step Solution:

  1. Use Taylor Expansion or Standard Limits: Near x=0x = 0, we can use approximations for small angles. Recall that:

    • cos(4x)1\cos(4x) \approx 1 for small xx,
    • tan(4x)4x\tan(4x) \approx 4x for small xx (since tan(x)x\tan(x) \approx x when x0x \to 0).
  2. Simplify the Expression: Substituting these approximations into the limit:

cos(4x)tan(4x)6x14x6x=4x6x=46=23\frac{\cos(4x) \cdot \tan(4x)}{6x} \approx \frac{1 \cdot 4x}{6x} = \frac{4x}{6x} = \frac{4}{6} = \frac{2}{3}

  1. Conclusion: The value of the limit is:

23\boxed{\frac{2}{3}}

Let me know if you would like more details or have any further questions!

Related Questions:

  1. How does the approximation tanxx\tan x \approx x work for small angles?
  2. Can we solve this limit using L'Hopital's Rule? How?
  3. What are some other common trigonometric limits near x=0x = 0?
  4. How do Taylor series expansions help in solving limits involving trigonometric functions?
  5. How does the result change if the angle inside the trigonometric functions is different (e.g., 2x2x instead of 4x4x)?

Tip: When dealing with trigonometric limits, small-angle approximations and standard limit rules like limx0sinxx=1\lim_{x \to 0} \frac{\sin x}{x} = 1 are often very useful!

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Limits
Small-Angle Approximations

Formulas

Limit approximation for small angles: \(\tan(x) \approx x\) and \(\cos(x) \approx 1\) for \(x \to 0\)
Simplification of trigonometric expressions
Standard limit: \( \lim_{x \to 0} \frac{\sin x}{x} = 1 \)

Theorems

Small Angle Approximation
Standard Trigonometric Limits

Suitable Grade Level

Grades 11-12, Pre-Calculus or Calculus I