... Theo chng minh phn a) suy c M1CM2 cõn ti C v cú gúc C = 12 00 Chng minh tng t suy c M1BM3 cõn ti B v cú gúc B = 12 00 Suy c M1CM2 v M1BM3 ng dng 2,0 1, 0 3,0 1, 0 1, 0 1, 0 RT KINH NGIM ... CM = CM2 (1) ã ã ã ã ã Mt khỏc: BCM1 = BCM v ACM = ACM = ACM ( t/c ) 1, 0 ã ã ã ã ã ã Suy đợc: BCM1 + BCM + ACM + ACM = 2.( BCM + ACM ) ã = ACB = 12 0 (1) T (1) v (2) suy c Q120 : M2 M1 C b) Theo ... x0; y0) Gi M1( x1; y1 ) l mt im tựy ý v M2( x2; y2) l nh ca im M1 qua phộp i xng tõm I Hóy tỡm h thc liờn h gia x1, y1, x2, y2, v x0, y0 ? y y2 y0 y1 M1 GV: CAO VN LIấM T KHTN M2 I 14 THPT TRNG...