Math Problem Statement

Evaluate \( \lim_{{x \to 0}} \frac{3x - \sin(2x)}{x \sin(x) + \ln(5x)} \).

Solution

The expression provided is:

limx03xsin(2x)xsin(x)+ln(5x)\lim_{{x \to 0}} \frac{3x - \sin(2x)}{x \sin(x) + \ln(5x)}

To solve this limit, let's analyze the behavior of the numerator and denominator as x0x \to 0:

Step 1: Analyze the Numerator

In the numerator, we have: 3xsin(2x)3x - \sin(2x) As x0x \to 0:

  1. 3x03x \to 0.
  2. sin(2x)2x\sin(2x) \approx 2x because sin(kx)kx\sin(kx) \approx kx for small xx.

So, 3xsin(2x)3x2x=x3x - \sin(2x) \approx 3x - 2x = x.

Step 2: Analyze the Denominator

In the denominator, we have: xsin(x)+ln(5x)x \sin(x) + \ln(5x) As x0x \to 0:

  1. xsin(x)xx=x2x \sin(x) \approx x \cdot x = x^2, since sin(x)x\sin(x) \approx x for small xx.
  2. ln(5x)\ln(5x) \to -\infty as x0x \to 0 from the positive side.

Thus, the denominator tends toward -\infty due to the ln(5x)\ln(5x) term.

Conclusion

Since the numerator approaches xx (a finite value) and the denominator approaches -\infty, the entire fraction approaches 00.

Therefore: limx03xsin(2x)xsin(x)+ln(5x)=0\lim_{{x \to 0}} \frac{3x - \sin(2x)}{x \sin(x) + \ln(5x)} = 0

Would you like further details on any steps, or have any questions?


Here are some related questions to consider:

  1. How does L'Hôpital's Rule apply to limits that approach an indeterminate form?
  2. What are some common approximations for trigonometric functions near zero?
  3. How does the natural logarithm function behave as its argument approaches zero from the right?
  4. Can this limit be solved using series expansion methods?
  5. What would happen if the denominator had a different logarithmic function, such as ln(x2)\ln(x^2)?

Tip: For limits involving sin(x)\sin(x) or ln(x)\ln(x), remember that small-angle approximations and logarithmic properties can simplify the calculations significantly.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric approximations
Logarithmic properties

Formulas

\( \sin(x) \approx x \) for small \( x \)
\( \ln(x) \to -\infty \) as \( x \to 0^+ \)

Theorems

Limit properties for trigonometric and logarithmic functions

Suitable Grade Level

Undergraduate Calculus or Advanced High School