計角度啊...點樣計??

a)∵BA//CO (已知)

∴∠AOC + 32°= 180°(同側內角)
∠AOC = 148°
∴優角AOC = 360°﹣148°(同頂角)

 = 212°

b)優角AOC = 2∠ABc (圓心角兩倍於圓周角)

212°= 2∠ABc

∠ABc = 212°/2

∠ABc = 106°


2008-01-24 20:48:40 補充：
∠ABC的C是大楷

a. ∵BA//CO
∴∠ABC+∠BCO=180° (同側內角和)
∴優角AOC=360°-180°-32°=148°
b. 連接AC
可得優角AOC=2 x ∠ABC (圓周角2倍於圓心角)
∴∠ABC=148°÷2=74°