Math Problem Statement

lim (1+x)^cotx

Solution

To solve the limit limx0(1+x)cot(x)\lim_{x \to 0} (1 + x)^{\cot(x)}, we'll proceed by first expressing the limit in a more convenient form.

Step 1: Rewrite the Expression

The given expression is (1+x)cot(x)(1 + x)^{\cot(x)}. We can rewrite this expression using the exponential function:

(1+x)cot(x)=ecot(x)ln(1+x)(1 + x)^{\cot(x)} = e^{\cot(x) \cdot \ln(1 + x)}

So, the limit becomes:

limx0(1+x)cot(x)=limx0ecot(x)ln(1+x)\lim_{x \to 0} (1 + x)^{\cot(x)} = \lim_{x \to 0} e^{\cot(x) \cdot \ln(1 + x)}

Step 2: Focus on the Exponent

Now, we need to evaluate the limit of the exponent cot(x)ln(1+x)\cot(x) \cdot \ln(1 + x) as xx approaches 0.

limx0cot(x)ln(1+x)\lim_{x \to 0} \cot(x) \cdot \ln(1 + x)

Recall that cot(x)=cos(x)sin(x)\cot(x) = \frac{\cos(x)}{\sin(x)}. Near x=0x = 0, cot(x)\cot(x) tends to 1x\frac{1}{x} because sin(x)x\sin(x) \approx x and cos(x)1\cos(x) \approx 1.

Thus:

limx0ln(1+x)x\lim_{x \to 0} \frac{\ln(1 + x)}{x}

Step 3: Apply L'Hôpital's Rule

The limit limx0ln(1+x)x\lim_{x \to 0} \frac{\ln(1 + x)}{x} is of the indeterminate form 00\frac{0}{0}, so we can apply L'Hôpital's Rule:

[ \lim_{x \to 0} \frac{\ln(1 + x)}{x} = \lim_{x \to 0} \frac{\frac{d}{dx}[\ln(1 + x)]}{\frac{d}{dx}[x]} = \lim_{x \to 0} \frac{\frac{1}{1+x}}{1} = \lim_{x \to 0} \frac{1}{1+x} = 1 ]

Step 4: Final Calculation

So, the limit of the exponent is:

limx0cot(x)ln(1+x)=limx0ln(1+x)x=1\lim_{x \to 0} \cot(x) \cdot \ln(1 + x) = \lim_{x \to 0} \frac{\ln(1 + x)}{x} = 1

Thus:

limx0(1+x)cot(x)=e1=e\lim_{x \to 0} (1 + x)^{\cot(x)} = e^1 = e

Final Answer:

limx0(1+x)cot(x)=e\lim_{x \to 0} (1 + x)^{\cot(x)} = e

Would you like more details on any part of this solution, or do you have any questions?

Here are some related questions to explore further:

  1. What is the derivative of ln(1+x)\ln(1 + x)?
  2. How does the limit limx0ln(1+x)x=1\lim_{x \to 0} \frac{\ln(1 + x)}{x} = 1 relate to the concept of the derivative?
  3. Can you apply L'Hôpital's Rule to other indeterminate forms?
  4. How would you solve this limit without using L'Hôpital's Rule?
  5. What happens if we change cot(x)\cot(x) to tan(x)\tan(x) in the original limit?
  6. How does this limit relate to the number ee?
  7. What are some other common limits that result in ee?
  8. How does the behavior of cot(x)\cot(x) as xx approaches 0 affect this limit?

Tip: When evaluating limits, especially those involving exponentials or logarithms, consider rewriting the expression using known limit properties or applying L'Hôpital's Rule if you encounter an indeterminate form.

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Math Problem Analysis

Mathematical Concepts

Limits
Exponential Functions
Logarithmic Functions
L'Hôpital's Rule

Formulas

Exponential function: $e^x$
L'Hôpital's Rule: $\lim_{x \to a} \frac{f(x)}{g(x)} = \lim_{x \to a} \frac{f'(x)}{g'(x)}$

Theorems

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Suitable Grade Level

Advanced High School / College