Answer:
arc length = 3π/4 cm
Explanation:
The appropriate relations are ...
... A = πr² . . . . area of a circle
so ...
... r = √(A/π)
and
... s = rθ . . . . . arc length
___
Combining these, we have
... s = θ√(A/π)
Filling in your numbers gives ...
... s = (π/4)√((9π cm²)/π)
... s = 3π/4 cm
