2 1 = 1 AOB = 22 2
AB CD CD AB O AB CD O
AOC = BOC = 1 AOB 2 AOC = BOC = 1 AOB 2
OA = OB = = AOC BOD SAS = OA = OB =
1 2
c = a + b- 1 2 2 2 2 4 ab = a + b 2
1.
2 3 1 2 3 1
1 ABC B = 45 BAC = 105 AB = 2 2 BC ABsinBAC BC = sinc = 2 2 sin 105 sin105 sin30 Rt ADC = 2 3 BC = BD + DC = 22 3 AD = 3x Rt ACD AD = CD = x + 2AC = 2x + 2 3x = 2 + x x = 3 +1 AB = 2x = 3 + 2 AC = 2x + 2 = 3 2 + 6
= = OA A B C D O OA