Q42 / 90 · KVPY 2011 (SB/SX) · Mathematics
Let $[x]$ denote the largest integer not exceeding $x$ and $\{x\}=x-[x]$. Then $\int_{0}^{2012} \frac{e^{\cos (\pi\{x\})}}{e^{\cos (\pi\{x\})}+e^{-\cos (\pi\{x\})}} d x$ is equal to -
- A0
- Correct answerB1006
- C2012
- D$2012 \pi$
Solution
$\mathrm{I}=2012 \int_{0}^{1} \frac{e^{\cos \pi x}}{e^{\cos \pi x}+e^{-\cos \pi x}} d x$
using king property $\mathrm{I}=2012 \int_{0}^{1} \frac{e^{-\cos \pi x}}{e^{-\cos \pi x}+e^{\cos \pi x}} d x \Rightarrow 2 \mathrm{I}=2012 \Rightarrow \mathrm{I}=1006$
Hence, the correct answer is option: 'B'.