Evaluate the following integral: `int_0^a x/(sqrt(a^2+x^2))dx`

Explanation

To evaluate the integral \( I = \int_0^a \frac{x}{\sqrt{a^2 + x^2}} \, dx \), we will use a substitution method.

### Step-by-step Solution:

1. **Substitution**: Let \( t = a^2 + x^2 \). Then, differentiating both sides gives:
\[ dt = 2x \, dx \quad \Rightarrow \quad x \, dx = \frac{dt}{2} \]
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