... Bng 2- 1 . DL2 3-6 > 6-8 > 8 -2 0 > ;2 0 -2 5 > ;2 5-3 2 >3 2- 4 0 b 2 3 4 5 6 7 B DL 2- 0 ,5 DL 2- 1 ,0 DL 2- 2 ,0 DL 2- 3 ,0 DL 2- 4 ,0 DL 2- 5 ,0 Kãút cáúu chäút trạm nhỉ hçnh 2- 2 1 : ... O2BC v O2AC ta cọ: 22 222 222 BCBOACAOCO −=−= (1) Trong âọ : ()2bLLBCABAC2DAOCL2L2+∆+∆=+== ( )22 L22D212dcBO ∆−== Hçnh 2- 2 0: så âäư tảo chäút vạt O1 O2 E D A B G F H C dc2 d‘c2 ... A B G F H C dc2 d‘c2 Dl2 Dl1 dc1 21 22 ∆L Z X b 32 Thay vo (1), ta âỉåüc : ( )22 22l2cL22L2b22D2bLL2D⎟⎠⎞⎜⎝⎛−⎟⎠⎞⎜⎝⎛∆−=⎥⎦⎤⎢⎣⎡+∆+∆−⎟⎠⎞⎜⎝⎛ B qua ( )22 2CL;LL ∆∆+∆ ...