Evaluate: `int_0^a(dx)/(x+sqrt((a^2-x^2)))orint_0^(pi/2)(d theta)/(1+tantheta)`

Explanation

To evaluate the integral

\[ I = \int_0^a \frac{dx}{x + \sqrt{a^2 - x^2}} \]

we will use the substitution \( x = a \sin \theta \).

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