Using the formula for area of a circle:
Area = pi x radius^2
Replace area with the given value:
39.62 = pi x radius^2
Divide both sides by pi
Radius^2 = 39.62/pi
Radius^2 = 12.62
Solve for radius by taking the square root of both sides
Radius = sqrt(12.62)
Radius = 3.55 cm