Evaluate the following integral :
`int(x+sqrt(a^(2)+x^(2)))^(2007)dx`

Explanation

To evaluate the integral \( \int (x + \sqrt{a^2 + x^2})^{2007} \, dx \), we will use a substitution method. Here are the steps:

### Step 1: Substitution
Let:
\[ t = x + \sqrt{a^2 + x^2} \]
From this substitution, we can express \( \sqrt{a^2 + x^2} \) in terms of \( t \):
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