... x g) cos2 x (cos2 x + sin x + sin x tan2 x ) = Tớnh cos180, sin720, sin1620, cos1620, sin1080, cos1080, tan720 Baứi Tỡm giỏ tr ln nht v giỏ tr nh nht ca biu thc: a) A = cos4 x cos2 x + sin ... r uu r r r uur b) Tớnh IJ, ú I, J c xỏc nh bi: IA + IB = 0, JB = JC HD: a) BC = 19 , AM = Baứi 10 Cho t giỏc ABCD b) IJ = 133 uuu uuu r r a) Chng minh AB BC + CD DA2 = AC.DB b) Suy iu kin ... ABC, bit: a) a = 14; b = 18; c = 20 c) a = 4; b = 5; c = b) b = 32; c = 45; = 870 A d) b = 14; c = 10; = 1450 A b) a = 6; b = 7,3; c = 4,8 d) a = 3; b = 2; c = BI TP ễN CHNG II Trang 92 Tớch vụ...