... dc = 011 b) Ggi G Id trgng tdm tam gidc ABC thi: HA + 'HB + 'HC = 3HG = 3 11 0 + 30G = 3 11 0 + 'dA + ^ + 'dc Kit hgp vdi kit qua cua cdu a), ta cd : HA + HB + HC = 3lld + 0H = 2lld 39 (h 21) Ggi ... 3.(B) 4.(D) (D) (A) (B) 8.(B) (C) 10 (D) 11 (A) 12 (C) 13 (A) 14 (B) 37 hiCdng IL TICH VO HlfdrNG CUA HAI VECTCf VA UING DUNG A €AC l&Sm THifC CO BAN VA BE BAI 1 Gia trj li/cfng giac cua mot goc ... G la trgng tdm tam giac A va M la trung dilm ciia DE thi vdi dilm / y, ta co : 1A + 1B + 1C + 1D + 1E = 31G + 21M Bdi vdy neu chgn / la trgng tdm cua he dilm A,B,C,D,E, tiic la trgng tdm cua...