Math Problem Statement

Evaluate the limit: \(\lim_{{x \to 0}} \frac{3x}{\sin(5x)}\)

Solution

The given expression is:

limx03xsin(5x)\lim_{{x \to 0}} \frac{3x}{\sin(5x)}

To evaluate this limit, we can apply the small-angle approximation:

limx0sin(kx)kx=1\lim_{{x \to 0}} \frac{\sin(kx)}{kx} = 1

Using this, let's manipulate the given expression. First, rewrite the limit in a more convenient form:

limx03xsin(5x)=limx03xsin(5x)\lim_{{x \to 0}} \frac{3x}{\sin(5x)} = \lim_{{x \to 0}} 3 \cdot \frac{x}{\sin(5x)}

Now, introduce the factor 5x5x inside the sine term by multiplying and dividing by 5:

=limx03x5x5xsin(5x)=limx0355xsin(5x)= \lim_{{x \to 0}} 3 \cdot \frac{x}{5x} \cdot \frac{5x}{\sin(5x)} = \lim_{{x \to 0}} \frac{3}{5} \cdot \frac{5x}{\sin(5x)}

Since limx05xsin(5x)=1\lim_{{x \to 0}} \frac{5x}{\sin(5x)} = 1, the expression simplifies to:

=351=35= \frac{3}{5} \cdot 1 = \frac{3}{5}

Thus, the value of the limit is:

35\boxed{\frac{3}{5}}

Would you like further clarification or details on this solution?

Related Questions:

  1. How does L'Hopital's rule work in this case?
  2. Can the small-angle approximation be used for other trigonometric functions?
  3. What is the behavior of sin(kx)\sin(kx) as x0x \to 0 for different values of kk?
  4. How would the limit change if the denominator was sin(3x)\sin(3x) instead of sin(5x)\sin(5x)?
  5. What happens if we don't use the small-angle approximation and apply a different method?

Tip:

For limits involving trigonometric functions near zero, the small-angle approximation is a very handy tool.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Functions
Small-Angle Approximation

Formulas

\(\lim_{{x \to 0}} \frac{\sin(kx)}{kx} = 1\)

Theorems

Small-Angle Approximation
Limit Theorems

Suitable Grade Level

Grades 11-12