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Evaluate : int [ log (log x) +(1)/((log ...

Evaluate : `int [ log (log x) +(1)/((log x)^(2)) ] dx`

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To evaluate the integral \[ \int \left( \log(\log x) + \frac{1}{(\log x)^2} \right) dx, \] we can break it down into two separate integrals: \[ \int \log(\log x) \, dx + \int \frac{1}{(\log x)^2} \, dx. \] ### Step 1: Evaluate \(\int \log(\log x) \, dx\) We will use integration by parts for this integral. Let: - \( u = \log(\log x) \) (First function) - \( dv = dx \) (Second function) Then, we differentiate \( u \) and integrate \( dv \): - \( du = \frac{1}{\log x} \cdot \frac{1}{x} \, dx = \frac{1}{x \log x} \, dx \) - \( v = x \) Using the integration by parts formula \(\int u \, dv = uv - \int v \, du\), we have: \[ \int \log(\log x) \, dx = x \log(\log x) - \int x \cdot \frac{1}{x \log x} \, dx. \] The integral simplifies to: \[ \int \log(\log x) \, dx = x \log(\log x) - \int \frac{1}{\log x} \, dx. \] ### Step 2: Evaluate \(\int \frac{1}{\log x} \, dx\) We will again use integration by parts. Let: - \( u = \frac{1}{\log x} \) - \( dv = dx \) Then, we differentiate \( u \) and integrate \( dv \): - \( du = -\frac{1}{(\log x)^2} \cdot \frac{1}{x} \, dx = -\frac{1}{x (\log x)^2} \, dx \) - \( v = x \) Using the integration by parts formula, we have: \[ \int \frac{1}{\log x} \, dx = x \cdot \frac{1}{\log x} - \int x \cdot \left(-\frac{1}{x (\log x)^2}\right) \, dx. \] This simplifies to: \[ \int \frac{1}{\log x} \, dx = \frac{x}{\log x} + \int \frac{1}{(\log x)^2} \, dx. \] ### Step 3: Substitute back Now substituting back into our original integral: \[ \int \log(\log x) \, dx = x \log(\log x) - \left( \frac{x}{\log x} + \int \frac{1}{(\log x)^2} \, dx \right). \] Combining everything, we have: \[ \int \left( \log(\log x) + \frac{1}{(\log x)^2} \right) dx = x \log(\log x) - \frac{x}{\log x} + \int \frac{1}{(\log x)^2} \, dx + \int \frac{1}{(\log x)^2} \, dx. \] The two integrals of \(\frac{1}{(\log x)^2}\) cancel each other out, leaving us with: \[ \int \left( \log(\log x) + \frac{1}{(\log x)^2} \right) dx = x \log(\log x) - \frac{x}{\log x} + C, \] where \(C\) is the constant of integration. ### Final Answer: \[ \int \left( \log(\log x) + \frac{1}{(\log x)^2} \right) dx = x \log(\log x) - \frac{x}{\log x} + C. \]
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