Answer:
The length of line AC is 6 units.
Explanation:
Given information: Angle A is circumscribed about circle O, AB=6 units anf radius of circle is 3 units.
Since A is circumscribed about circle O, it means AC and AB are tangents to circle.
According to the Circle Theorem, tangents from the same point have the same length.
AC and AB are tangents on the circle from point A, so
![AC=AB](https://img.qammunity.org/2020/formulas/mathematics/middle-school/7js0ixhddt6uhvwfzmoxblzdjjasdizmh7.png)
![AC=6](https://img.qammunity.org/2020/formulas/mathematics/middle-school/juv8v6qj46md519o3eus1ihjt42mbj9eb3.png)
Therefore the length of line AC is 6 units.