Evaluate: `int(1-tanx)/(1+tanx)\ dx`

Explanation

To evaluate the integral \(\int \frac{1 - \tan x}{1 + \tan x} \, dx\), we can follow these steps:

### Step 1: Rewrite the integral
We start with the integral:
\[ I = \int \frac{1 - \tan x}{1 + \tan x} \, dx \]

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