Evaluate: `intsqrt((1+x)/(1-x))dx`

Explanation

To evaluate the integral \(\int \sqrt{\frac{1+x}{1-x}} \, dx\), we will follow a systematic approach.

### Step 1: Rationalize the integrand
We start by rewriting the integrand:
\[ \sqrt{\frac{1+x}{1-x}} = \frac{\sqrt{(1+x)(1+x)}}{\sqrt{(1-x)(1+x)}} = \frac{1+x}{\sqrt{1-x^2}} \]
Thus, we can rewrite the integral as:
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