Câu fifteen. ?? dài trung tuy?n mc ?ng v?i c?nh c c?a DABC b?ng bi?u th?c nào sau ?âyT?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 12T?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 twelveH? tr?i nghi?m, h??ng nghi?p 6 SGK Tr?i nghi?m, h??ng ngh