Created by the Canadian IMO team during their summer training, to challenge each other.

1.在$\triangle ABC$中,$\angle BAC=60^{\circ}$且内切圆分别切$AB,AC$于$P,Q$.$PC,QB$交于点$G$.设$r$为$\triangle BCG$的外接圆半径,求$\displaystyle \frac{r}{BC}$的最小值. 继续阅读 →