Question

如图,圆O的半径为4CM,弦AB的弦心距OM为2CM,C D分别是劣弧

Answer 1

因为,OA=4,OM=2,

即有：cos∠AOM = 2/4 = 1/2 ,

所以,∠AOM = 60°,∠AOB = 2∠AOM = 120°.

可得：∠ADB = (1/2)∠AOB = 60°,∠ACB = 180°-∠ADB = 120°.