Radius = 42/(2*pi) = 6.68450761
Area = pi*6.684507612 = 140.375 square units rounded to 3 decimal places
A part of a circle's circumference is an arc
The distance around a circle is its' circumference.
140.37 square units.
It is not clear whether you want the formula of some aspect (area or circumference) of a circle when given its radius or a formula for its radius when given some characteristic measure of the circle.
Your question is incomplete. The circumference of 42 is 42!
140.4 square units.
Using 3.14 as Pi the area of circle is: 0
The radius of a circle if its circumference is 42 is about 6.68
140.37 units squaredThe area of this circle is: 140.37 units2
Area = pi*23 squared = 1661.902514 or 1662 square cm rounded
Circumference = Pi x d: 42 = 3.14 x 42 = 131.88 feet
The circumference of a 42-inch diameter circle is: ~131.95 inches.