Math Problem Statement

Tentukan limitnya

Tentukan limitnya

Solution

Let’s solve the two limits from the image step by step.

1. limx21x+12x3+8\lim_{x \to 2} \frac{\frac{1}{x} + \frac{1}{2}}{x^3 + 8}

Solution:

First, simplify the numerator.

1x+12=2+x2x\frac{1}{x} + \frac{1}{2} = \frac{2 + x}{2x}

Thus, the expression becomes:

limx22+x2xx3+8\lim_{x \to 2} \frac{\frac{2 + x}{2x}}{x^3 + 8}

Notice that x3+8x^3 + 8 can be factored as a sum of cubes:

x3+8=(x+2)(x22x+4)x^3 + 8 = (x + 2)(x^2 - 2x + 4)

Now, substitute x=2x = 2 directly in the limit since the function is defined at x=2x = 2:

2+22223+8=448+8=116\frac{\frac{2 + 2}{2 \cdot 2}}{2^3 + 8} = \frac{\frac{4}{4}}{8 + 8} = \frac{1}{16}

So, the limit is:

116\boxed{\frac{1}{16}}


2. limx0tan(5x)sin(2x)\lim_{x \to 0} \frac{\tan(5x)}{\sin(2x)}

Solution:

For small xx, we can use the approximations:

tan(5x)5xandsin(2x)2x\tan(5x) \approx 5x \quad \text{and} \quad \sin(2x) \approx 2x

Thus, the expression becomes:

limx05x2x\lim_{x \to 0} \frac{5x}{2x}

Canceling xx (as long as x0x \neq 0):

limx052=52\lim_{x \to 0} \frac{5}{2} = \frac{5}{2}

So, the limit is:

52\boxed{\frac{5}{2}}


Do you need further clarifications or details?


5 Related Questions:

  1. How do you apply L'Hôpital's rule to evaluate limits?
  2. What is the approximation for trigonometric functions near 0?
  3. How do you factor sums and differences of cubes?
  4. When can direct substitution be used to evaluate limits?
  5. How are limits involving indeterminate forms handled?

Tip: For complicated limits, always check if factoring or approximations simplify the problem before applying advanced methods like L’Hôpital’s rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Limits
Algebraic Simplification
Limit Approximations

Formulas

Limit of rational functions as x approaches a value
Approximations for trigonometric functions near 0: tan(x) ≈ x, sin(x) ≈ x

Theorems

Sum of cubes
Limit properties and trigonometric approximations

Suitable Grade Level

Grade 12 or College Level