Math Problem Statement

Limit x tends 0+ (sinx)^x

Solution

To find the limit of limx0+(sinx)x\lim_{x \to 0^+} (\sin x)^x, we can approach the problem step by step.

Step 1: Express the limit in a more manageable form

We start by expressing the given limit:

limx0+(sinx)x\lim_{x \to 0^+} (\sin x)^x

Since directly evaluating the expression might be challenging, we can take the natural logarithm of the expression. This will allow us to simplify the exponentiation:

y=(sinx)xy = (\sin x)^x

Now take the natural logarithm of both sides:

lny=ln((sinx)x)=xln(sinx)\ln y = \ln\left( (\sin x)^x \right) = x \ln(\sin x)

Thus, we need to find the limit of xln(sinx)x \ln(\sin x) as x0+x \to 0^+.

Step 2: Evaluate the limit of xln(sinx)x \ln(\sin x)

We know that sinxx\sin x \approx x when xx is close to 0, so we can approximate ln(sinx)\ln(\sin x) by ln(x)\ln(x) for small values of xx. Therefore, the limit becomes:

limx0+xln(sinx)limx0+xln(x)\lim_{x \to 0^+} x \ln(\sin x) \approx \lim_{x \to 0^+} x \ln(x)

Step 3: Evaluate the limit of xln(x)x \ln(x)

We can evaluate the limit of xln(x)x \ln(x) using L'Hopital's Rule. The limit is of the indeterminate form 0×()0 \times (-\infty), so we rewrite it as a fraction:

limx0+xln(x)=limx0+ln(x)1/x\lim_{x \to 0^+} x \ln(x) = \lim_{x \to 0^+} \frac{\ln(x)}{1/x}

Now apply L'Hopital's Rule. Differentiate the numerator and denominator:

limx0+1/x1/x2=limx0+x=0\lim_{x \to 0^+} \frac{1/x}{-1/x^2} = \lim_{x \to 0^+} -x = 0

Thus:

limx0+xln(x)=0\lim_{x \to 0^+} x \ln(x) = 0

Step 4: Conclude the original limit

Since xln(sinx)0x \ln(\sin x) \to 0, we have:

limx0+lny=0\lim_{x \to 0^+} \ln y = 0

Exponentiating both sides:

y=e0=1y = e^0 = 1

Thus:

limx0+(sinx)x=1\lim_{x \to 0^+} (\sin x)^x = 1

Final Answer:

limx0+(sinx)x=1\lim_{x \to 0^+} (\sin x)^x = 1

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

Here are some related questions you might find interesting:

  1. How does L'Hopital's Rule apply to indeterminate forms?
  2. What is the approximation sinxx\sin x \approx x valid for?
  3. How can we use logarithms to simplify limits involving exponents?
  4. How do we handle limits involving natural logarithms and small values of xx?
  5. Can you compute limits of the form 0×()0 \times (-\infty) without L'Hopital's Rule?

Tip: When dealing with limits involving exponentiation or small values of xx, taking the logarithm often simplifies the expression and makes the limit easier to evaluate.

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Math Problem Analysis

Mathematical Concepts

Limits
Logarithms
Exponentiation
Indeterminate Forms
L'Hopital's Rule

Formulas

\lim_{x \to 0^+} (\sin x)^x
\ln(\sin x)
\lim_{x \to 0^+} x \ln(x)
L'Hopital's Rule: \lim_{x \to 0^+} \frac{f(x)}{g(x)} = \lim_{x \to 0^+} \frac{f'(x)}{g'(x)}

Theorems

Indeterminate forms and L'Hopital's Rule
Logarithmic properties for limits

Suitable Grade Level

Grades 11-12