Evaluate: `int_0^(pi//4)tan^2x dx`

Explanation

To evaluate the integral \( \int_0^{\frac{\pi}{4}} \tan^2 x \, dx \), we can follow these steps:

### Step 1: Use the identity for \( \tan^2 x \)
We know from trigonometric identities that:
\[ \tan^2 x = \sec^2 x - 1 \]
Thus, we can rewrite the integral as:
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