The name of a circle is the name of its center. So the center of circle A is the point A. This makes angle PAC a central angle. This is important because we will be using the following proportion which connects central angles and the their related arcs:
part Central Angle length of arc
----- = ------------- = ----------------
whole 360
Putting the given angle and radius we get:
The left side reduces to:
Cross-multiplying we get:
Dividing by 12:
which reduces to:
or