Question
Evalute the following integrals:
$\int\frac{1}{\text{x}(3+\log\text{x})}\text{dx}$

Answer

Here, we are considering $\log\text{x}$ as $\log_\text{e}\text{x}$.

Let $\text{I}=\int\frac{1}{\text{x}(3+\log\text{x})}\text{dx}$

Putting $\log\tan\text{x}=\text{t}$

$\Rightarrow\frac{1}{\text{x}}=\frac{\text{dt}}{\text{dx}}$

$\Rightarrow\frac{\text{dx}}{\text{x}}=\text{dt}$

$\therefore\text{I}=\int\frac{\text{dt}}{3+\text{t}}$

$=\log|3+\text{t}|+\text{C}$

$=\log|3+\log\text{x}|+\text{C}\ \big[\because\text{t}=\log\text{x}\big]$

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