Correct option: A.$\int\limits_0^{\log \left( {1 + \sqrt 2 } \right)} {2{{\left( {{e^u} + {e^{ - u}}} \right)}^{16}}du} $
A $I=\int_{\frac{\pi}{4}}^{\frac{\pi}{2}} (2\cos ecx)^{17}dx$
$=\int_{\frac{\pi}{4}}^{\frac{\pi}{2}} 2^{17}(2\cos ecx)^{16}\cos ecx \ dx$
અહી,$\cos ecx+\cot x=t$
=$-\cos ecxdx=\frac{dt}{\cos ecx+\cot x}$
તથા
$\begin{cases}x=\frac{\pi}{4}\Rightarrow &t=\sqrt{2}+1\\x=\frac{\pi}{2}\Rightarrow &t=1\end{cases}$
$I=\int_{\sqrt{2}+1}^{'} -2^{17}\left(\frac{t+\frac{1}{t}}{2}\right)^{16}\frac{dt}{t}$
અહી$t=e^u$
$at=e^udu$
$\begin{cases}t=1, & u = 0\\t=\sqrt{2}+1, &u=\log(\sqrt{2}+1)\end{cases}$
$I=-\int_{\log\sqrt{2}+1}^{0} 2(e^u+e^{-u})^{16}\frac{e^udu}{e^u}$.
$I=\int_{\log\sqrt{2}+1}^{0} 2(e^u+e^{-u})^{16}du$
$I=\int_{0}^{\log\sqrt{2}+1} 2(e^u+e^{-u})^{16}du$