Evaluate the following integral: `int_0^(pi//4)tan^4x\ dx`

Explanation

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

### Step 1: Rewrite the Integral
We start by rewriting \( \tan^4 x \) in terms of \( \tan^2 x \):
\[ I = \int_0^{\frac{\pi}{4}} \tan^2 x \cdot \tan^2 x \, dx \]
Using the identity \( \tan^2 x = \sec^2 x - 1 \), we can express the integral as:
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