It's easy if you remember the formulas you learned for the area, diameter,
and circumference of a circle:
-- Area = (pi) (radius)²
-- Diameter = (2) (radius)
-- Circumference = (pi) (diameter)
You know the area. So let's use the first formula to find the circle's radius.
Area = (pi) (radius)²
Divide each side by (pi): Area/pi = (radius)²
Radius = √(area/pi)
Now use the second formula to find the circle's diameter:
Diameter = (2) (radius)
Diameter = 2 √(area/pi)
Now use the third formula to find the circle's circumference:
Circumference = (pi) (diameter)
Circumference = (pi) (2) √(area/pi)
With just a little tweak, that can be written slightly more simply:
Circumference = 2 √(pi x area)
See ? Just the three circle formulas,and a lot of massaging.
