Math Problem Statement

lim (x → 0) (√(sin x)) / (sin(√x))

Solution

The given limit is:

limx0sinxsin(x)\lim_{x \to 0} \frac{\sqrt{\sin x}}{\sin (\sqrt{x})}

To solve this limit:

  1. First step: Check direct substitution. When x=0x = 0, sin0=0=0\sqrt{\sin 0} = \sqrt{0} = 0 and sin(0)=sin(0)=0\sin (\sqrt{0}) = \sin(0) = 0 So, the expression gives a form of 00\frac{0}{0}, which is an indeterminate form. This suggests we can apply L'Hopital's Rule.

  2. Applying L'Hopital's Rule: Since the limit is in the indeterminate form 00\frac{0}{0}, we can differentiate the numerator and denominator separately with respect to xx.

    • Differentiate the numerator: ddx(sinx)=12sinxcosx\frac{d}{dx} \left( \sqrt{\sin x} \right) = \frac{1}{2\sqrt{\sin x}} \cdot \cos x

    • Differentiate the denominator: ddx(sin(x))=cos(x)12x\frac{d}{dx} \left( \sin(\sqrt{x}) \right) = \cos(\sqrt{x}) \cdot \frac{1}{2\sqrt{x}}

  3. Substitute these into L'Hopital's Rule: The new limit becomes: limx012sinxcosxcos(x)12x\lim_{x \to 0} \frac{\frac{1}{2\sqrt{\sin x}} \cdot \cos x}{\cos(\sqrt{x}) \cdot \frac{1}{2\sqrt{x}}}

    Simplifying the constants: limx0xcosxsinxcos(x)\lim_{x \to 0} \frac{\sqrt{x} \cdot \cos x}{\sqrt{\sin x} \cdot \cos(\sqrt{x})}

  4. Evaluate the limit as x0x \to 0:

    • cos(0)=1\cos(0) = 1, so the cosine terms approach 1.
    • As x0x \to 0, sinxx\sin x \approx x, so sinxx\sqrt{\sin x} \approx \sqrt{x}.

    Therefore, the limit simplifies to: limx0xx=1\lim_{x \to 0} \frac{\sqrt{x}}{\sqrt{x}} = 1

Thus, the value of the limit is: 1\boxed{1}

Would you like further clarification or details on any part of the process?

Relative Questions:

  1. What conditions allow the use of L'Hopital's Rule?
  2. How does the approximation sinxx\sin x \approx x help in limit evaluations?
  3. What are other methods besides L'Hopital's Rule to solve indeterminate forms?
  4. Can the limit be solved using series expansions?
  5. How do we differentiate composite functions like sin(x)\sin(\sqrt{x})?

Tip:

For limits involving trigonometric functions near 0, small-angle approximations (like sinxx\sin x \approx x) are often very useful for simplifying expressions.

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Math Problem Analysis

Mathematical Concepts

Limits
L'Hopital's Rule
Trigonometric Functions
Differentiation

Formulas

L'Hopital's Rule
Small-angle approximation: sin(x) ≈ x when x → 0

Theorems

L'Hopital's Rule

Suitable Grade Level

Grades 11-12 (Calculus)