Math Problem Statement

Evaluate the limit as x approaches 0 for the expression (x^2 * sin(x) * (1/2) * sin(x) * sqrt(x)) / x^3.

Solution

The given limit expression is:

limx0x2sin(x)(12)sin(x)xx3\lim_{x \to 0} \frac{x^2 \sin(x) \left(\frac{1}{2} \right) \sin(x) \sqrt{x}}{x^3}

Let's simplify the expression step by step:

  1. The expression in the numerator is: x2sin(x)12sin(x)xx^2 \sin(x) \cdot \frac{1}{2} \cdot \sin(x) \sqrt{x} This can be rewritten as: 12x2sin(x)sin(x)x\frac{1}{2} x^2 \sin(x) \sin(x) \sqrt{x} Which simplifies to: 12x2sin2(x)x\frac{1}{2} x^2 \sin^2(x) \sqrt{x}

  2. The full expression for the limit becomes: limx012x2sin2(x)xx3\lim_{x \to 0} \frac{\frac{1}{2} x^2 \sin^2(x) \sqrt{x}}{x^3}

  3. Simplify the fraction: 12x2sin2(x)xx3=12sin2(x)xx\frac{\frac{1}{2} x^2 \sin^2(x) \sqrt{x}}{x^3} = \frac{1}{2} \cdot \frac{\sin^2(x) \sqrt{x}}{x}

  4. Now, as x0x \to 0, we know that: limx0sin(x)x=1\lim_{x \to 0} \frac{\sin(x)}{x} = 1 So, using this fact, we can approximate sin2(x)\sin^2(x) near zero: sin2(x)x21\frac{\sin^2(x)}{x^2} \approx 1

  5. Therefore, the limit becomes: limx012sin2(x)xx=120=0\lim_{x \to 0} \frac{1}{2} \cdot \frac{\sin^2(x) \sqrt{x}}{x} = \frac{1}{2} \cdot 0 = 0

Thus, the value of the limit is:

0\boxed{0}

Would you like more details on any step? Here are some related questions:

  1. How do we apply limits involving trigonometric functions like sin(x)\sin(x)?
  2. Why does limx0sin(x)x=1\lim_{x \to 0} \frac{\sin(x)}{x} = 1 hold?
  3. What are other methods to simplify limits involving sin(x)\sin(x)?
  4. How does L'Hopital's Rule apply to this kind of limit problem?
  5. Could Taylor series expansions help simplify this expression?

Tip: When working with limits involving trigonometric functions, knowing common limits like limx0sin(x)x\lim_{x \to 0} \frac{\sin(x)}{x} can save time!

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry

Formulas

lim (sin(x)/x) as x -> 0 = 1

Theorems

Small-angle approximation for sine

Suitable Grade Level

University level (Calculus)