+129850 AC is a diameter
arc ABC =180
angle ABC measures (1/2) of this arc = 90
minor arc BC = 2 * minor arc AB
So let minor arc AB = x
So minor arc BC = 2x
So minor arc AB + minor arc BC =180
x + 2x = 180
3x = 180
x = 180/3 = 60
If minor arc AB = 60 then angle ACB is (1/2) of this = 30
