12/13cosa-5/13sina=33/65
12/13cosa=5/13sina+33/65
cosa=5/12sina+11/20
cos²a=25/144sin²a+121/400+11/24sina
sin²a+cos²a=25/144sin²a+121/400+11/24sina+sin²a
169/144sin²a+11/24sina-279/400=0
sin²a+66/169sina-279/400
解方程就是
楼主题目有问题,不会有这样变态计算在
12/13cosa-5/13sina=33/65
12/13cosa=5/13sina+33/65
cosa=5/12sina+11/20
cos²a=25/144sin²a+121/400+11/24sina
sin²a+cos²a=25/144sin²a+121/400+11/24sina+sin²a
169/144sin²a+11/24sina-279/400=0
sin²a+66/169sina-279/400
解方程就是
楼主题目有问题,不会有这样变态计算在