Cho tam giác ABC.BC=a,CA=b,AB=c và r là đọ dài bán kính nội tiếp.
CMR: $\frac{1}{sin\frac{A}{2}}+\frac{1}{sin\frac{B}{2}}+\frac{1}{sin\frac{C}{2}}\leq \frac{\sqrt{ab+bc+ca}}{r}$
$\frac{1}{sin\frac{A}{2}}+\frac{1}{sin\frac{B}{2}}+\frac{1}{sin\frac{C}{2}}\leq
Started By cuongcute1234, 04-12-2013 - 20:14
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