(a) Evaluate : $\int_{0}^{\frac{\pi}{4}} \frac{x \, dx}{1 + \cos 2x + \sin 2x}$ OR (b) Find : $\int e^{x} \left[ \frac{1}{(1 + x^{2})^{\frac{3}{2}}} + \frac{x}{\sqrt{1 + x^{2}}} \right] dx$.