$\int\limits_{-2}^2 \min (x-[x],-x-[-x]) d x$, where [.] is the greatest integer function = |
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Let $I=\int\limits_{-2}^2 \min (x-[x],-x-[-x]) d x$ $=2 \int\limits_0^2 \min (x-[x],-x-[-x]) d x$ (∵ function is even) $\min (x-[x],-x-[-x])=\left\{\begin{array}{l}x, 0 \leq x<\frac{1}{2} \\ -x+1, \frac{1}{2} \leq x<1 \\ x-1,1 \leq x<\frac{3}{2} \\ -x+2, \frac{3}{2} \leq x<2\end{array}\right.$ ∴ $I=2 \int\limits_0^{\frac{1}{2}} x d x+2 \int\limits_{\frac{1}{2}}^1(-x+1) d x+2 \int\limits_1^{\frac{3}{2}}(x-1) d x+ 2 \int\limits_{\frac{3}{2}}^2(-x+2) d x$ $=2\left[\frac{x^2}{2}\right]_0^{\frac{1}{2}}+2\left[-\frac{x^2}{2}+x\right]_{\frac{1}{2}}^1+2\left[\frac{x^2}{2}-x\right]_1^{\frac{3}{2}}+2\left[-\frac{x^2}{2}+2 x\right]_{\frac{3}{2}}^2$ $=\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}=1$ Hence $I = 1$ |