Step-by-Step Solution
Key Concept: Apply $\int_0^\pi f(x) \, dx = \int_0^\pi f(\pi - x) \, dx$, add this to the original integral, and you will be left with an integral of $\frac{1}{1 + \sin x}$ alone.
The detailed step-by-step mathematical proof is available inside the Mathbee app workspace.
Correct Answer: (1)