“ｃｏｓθ＝ｃｏｓθ１·ｃｏｓθ２”又一新的认识及应用王满成（湖南城步教研室）下面这个教材上的好习题．其多方面应用可见之于各种中学数学期刊．笔者在反复的教学过程中，又获得了对该题结论的一个新的应用功能，颇具新意．欣喜之余，特奉献出来与同行们共赏．习题... Another new understanding and application of “cosθ=cosθ1·cosθ2” is Wang Mancheng (Hunan Chengbu Teaching and Research Office). Here is a good exercise on this textbook. Its various applications can be seen in various middle school mathematics journals. In the course of repeated teaching, the author obtained a new application function of the conclusion of the title, which is quite new. Exultation, special offer to share with colleagues. exercise...