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Math

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PROBLEM

limx0+(tanxlnx)\lim _{x \rightarrow 0^{+}}(\tan x \cdot \ln x)

STEP 1

1. We are dealing with a limit problem involving a product of two functions: tanx\tan x and lnx\ln x.
2. The limit is taken as xx approaches 00 from the positive side, denoted by 0+0^+.
3. The function lnx\ln x approaches -\infty as xx approaches 0+0^+, and tanx\tan x approaches 00.

STEP 2

1. Analyze the behavior of tanx\tan x and lnx\ln x as x0+x \to 0^+.
2. Use limit properties or transformations to evaluate the limit.
3. Conclude the result of the limit.

STEP 3

First, analyze the behavior of each function separately as x0+x \to 0^+.
- tanx\tan x approaches 00 as xx approaches 00 from the positive side.
- lnx\ln x approaches -\infty as xx approaches 0+0^+.

STEP 4

Since the limit involves an indeterminate form 0()0 \cdot (-\infty), we need to transform it into a form suitable for L'Hôpital's Rule or another method.
Rewrite the expression tanxlnx\tan x \cdot \ln x as:
lnxcotx\frac{\ln x}{\cot x} Now, as x0+x \to 0^+, lnx\ln x \to -\infty and cotx\cot x \to \infty, resulting in the indeterminate form \frac{-\infty}{\infty}.

STEP 5

Apply L'Hôpital's Rule, which is applicable for indeterminate forms \frac{\infty}{\infty} or 00\frac{0}{0}.
Differentiate the numerator and the denominator:
- The derivative of lnx\ln x is 1x\frac{1}{x}.
- The derivative of cotx\cot x is csc2x-\csc^2 x.
Apply L'Hôpital's Rule:
limx0+lnxcotx=limx0+1xcsc2x\lim_{x \to 0^+} \frac{\ln x}{\cot x} = \lim_{x \to 0^+} \frac{\frac{1}{x}}{-\csc^2 x} Simplify:
=limx0+sin2xx= \lim_{x \to 0^+} \frac{-\sin^2 x}{x}

STEP 6

Evaluate the limit:
As x0+x \to 0^+, sinxx\sin x \approx x, so sin2xx2\sin^2 x \approx x^2.
limx0+sin2xx=limx0+x2x=limx0+x=0\lim_{x \to 0^+} \frac{-\sin^2 x}{x} = \lim_{x \to 0^+} \frac{-x^2}{x} = \lim_{x \to 0^+} -x = 0

SOLUTION

Conclude the result of the limit:
The limit is:
0\boxed{0}

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