Question

AB切圆o于C,AO交圆o于D,AO的延长线交圆o于E若角A为40度,求弧EMC度数

Answer 1

连接OC ,则有：OC⊥AB ,

可得：∠AOC = ∠OCB - ∠A = 90°- x ,

因为,OC = OE ,

所以,∠AEC = (1/2)∠AOC = 45°- (1/2)x ,

可得：∠ECB = ∠A ∠AEC = 45° (1/2)x