Question

[Fan EBXTOS]

Cho tam giác ABCcó AB=a,AC=b,BC=c

a,C/m:\(sin\frac{A}{2}\le\frac{a}{b+c}\)

b,C/m:\(sin\frac{A}{2}.sin\frac{B}{2}.sin\frac{C}{2}\le\frac{1}{8}\)