Step 1: Relating the two integrals.
We are given two integrals \( I_1 \) and \( I_2 \). Let us first examine \( I_1 \):
\[
I_1 = \int_{\alpha}^{\pi - \alpha} x \sin x \, dx
\]
We can split the limits of the integral and compute the value of \( I_2 \).
Step 2: Rewriting the integrals.
\( I_2 \) represents the integration of a function of \( \sin x \), so from previous results we have:
\[
I_2 = 2 I_1
\]
Step 3: Conclusion.
Thus, \( I_2 \) is equal to \( 2 I_1 \), which matches option (C).