Evaluate: `int(log(1+x^2))/(x^3)\ dx`

Explanation

To evaluate the integral \( I = \int \frac{\log(1+x^2)}{x^3} \, dx \), we will use substitution to simplify the integration process.

### Step-by-Step Solution:

1. **Substitution**: Let \( t = \frac{1}{x^2} \). Then, we differentiate to find \( dx \):
\[ dt = -\frac{2}{x^3} \, dx \implies dx = -\frac{x^3}{2} \, dt \]
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