The formula for the circumference of a circle is
C=πd where d=diameter
The line segment AC would be the diameter of the circle, but in order to solve for it, since its the hypotenuse of a right triangle, we need to use the pythagorean theorem.
a²+b²=c²
6²+8²=c²
36+64=c²
100=c²
√100=c
10=c
So line segment AC is 10 units long. The diameter is 10 units long. Now we can solve for the circumference
C=πd
C=10π
Since they asked for the EXACT circumference, we can stop here.
Answer=10π