Question Number 172694 by Shrinava last updated on 30/Jun/22
$$\mathrm{I}-\mathrm{incenter} \\ $$$$\mathrm{AB}\:,\:\mathrm{BE}\:,\:\mathrm{CF}-\mathrm{internal}\:\mathrm{bisectors}\:\mathrm{in}\:\bigtriangleup\mathrm{ABC} \\ $$$$\mathrm{Prove}\:\mathrm{that} \\ $$$$\mathrm{8}\:\leqslant\:\frac{\mathrm{AI}}{\mathrm{DI}}\:\centerdot\:\frac{\mathrm{BI}}{\mathrm{EI}}\:\centerdot\:\frac{\mathrm{CI}}{\mathrm{FI}}\:\leqslant\:\frac{\mathrm{4R}}{\mathrm{r}} \\ $$