11. The value of $\int - ח ( \cos 2 x / 1 + a x ) d x , a > 0$, is \section*{III askllTians ||} ... Powered By IITians\\ (A) $\sqcap$\\ (B) ап\\ (C) $\pi / 2$\\ (D) $2 \sqcap$\\