(begin array l Rightarrow sin Acos C + sin Ccos A = 2cos Asin C Leftrightarrow sin Acos C = cos Asin C;(*)finish array ) T?t C?Tin H?c L?p 6Tin H?c L?p 7Tin H?c L?p 8Tin H?c L?p 9Tin H?c L?p 10Tin H?c L?p 11Tin H?c L?p 12 T?t C?Th? D?c L?p tenth? D?c L?p eleventh? D?c L?p 12Th? D?c L?p sixth?