∑cos^3A／2＜2与Kooistra不等式

On  cos 3 A2<2 and Kooistra's Inequality

证明了若－π≤Ａ，Ｂ，Ｃ≤π且Ａ＋Ｂ＋Ｃ＝π，则（４＋２３）ｃｏｓ３Ａ２＋（５－２３）ｃｏｓ２Ａ２≤１８。

It was proved that for any A,B,C which satisfies -π≤ A,B,C ≤π and A +B+C=π, (4+23)  cos 2A2≤18 . Then the conjecture:  cos 3A2 <2 made by Chen Ji in 1992 was deduced and the Kooistra's inequality  cos 2A2 >2 was also extended.