Cho tam giác ABC bất kỳ. Khảng định hay phủ định :
$(1+cos \frac{A}{2})(1+cos \frac{B}{2})(1+cos\frac{C}{2})> 4$
$(1+cos \frac{A}{2})(1+cos \frac{B}{2})(1+cos\frac{C}{2})> 4$
Started By cuongcute1234, 22-11-2013 - 14:13
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