Answer:
200°
Step-by-step explanation:
In ΔABO ∠ABO=20°/2=10°
∠BAO=90°
sum of the angles of the ΔABO=180°
90°+10°+x=180°
x=180°-100°=80°
Therefore ∠AOB=80°
By similarity we have ∠COB=∠AOB=80°
Let the arc AC be x
now we know that the whole angle is 360°
x+80°+80°=360°
x=200°
