1. **State the problem:** Evaluate the limit $$\lim_{x \to 0} (1 + \tan x)^{\cot x}$$.
2. **Recall the formula and rules:** This is a limit of the form $$\lim_{x \to 0} (1 + f(x))^{g(x)}$$ which often can be evaluated using the exponential and logarithm transformation:
$$\lim_{x \to 0} (1 + f(x))^{g(x)} = e^{\lim_{x \to 0} g(x) \ln(1 + f(x))}$$.
3. **Apply the transformation:** Let $$f(x) = \tan x$$ and $$g(x) = \cot x = \frac{\cos x}{\sin x}$$.
We write:
$$\lim_{x \to 0} (1 + \tan x)^{\cot x} = e^{\lim_{x \to 0} \cot x \cdot \ln(1 + \tan x)}$$.
4. **Evaluate the inner limit:**
As $$x \to 0$$, $$\tan x \approx x$$ and $$\ln(1 + \tan x) \approx \tan x$$ because $$\ln(1 + y) \approx y$$ for small $$y$$.
So,
$$\cot x \cdot \ln(1 + \tan x) \approx \frac{\cos x}{\sin x} \cdot \tan x = \frac{\cos x}{\sin x} \cdot \frac{\sin x}{\cos x} = 1$$.
5. **Confirm the limit:**
More rigorously,
$$\lim_{x \to 0} \cot x \cdot \ln(1 + \tan x) = \lim_{x \to 0} \frac{\cos x}{\sin x} \cdot \ln(1 + \tan x)$$
Using the approximations:
$$\cot x \approx \frac{1}{x}$$
$$\ln(1 + \tan x) \approx x$$
So,
$$\lim_{x \to 0} \cot x \cdot \ln(1 + \tan x) = \lim_{x \to 0} \frac{1}{x} \cdot x = 1$$.
6. **Final answer:**
$$\lim_{x \to 0} (1 + \tan x)^{\cot x} = e^{1} = e$$.
Limit Tan Cot 68D214
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