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1987年,苏化明未加证明地介绍了如下不等式链:在△ABC中,有 -cos2A-cos2B-cos2C ≤cosA+cosB+cosC ≤sinA/2+sinB/2+sinC/2 ≤3/2. (1) 杨学枝老师在文中给出了△ABC中的一个不等式: sin~2A/2+sin~2B/2+sin~2C/2≤1/4 (ctgB/2ctgC/2+ctgC/2ctgA/2+ctgA/2ctgB/2)~(1/2) (2)
In 1987, Su Huaming did not prove the following inequality chain: In △ABC, there are -cos2A-cos2B-cos2C ≤cosA+cosB+cosC ≤sinA/2+sinB/2+sinC/2 ≤3/2. ( 1) Teacher Yang Xuezhi gives an inequality in △ABC: sin~2A/2+sin~2B/2+sin~2C/2≤1/4 (ctgB/2ctgC/2+ctgC/2ctgA/2+ ctgA/2ctgB/2)~(1/2) (2)