In order to calculate the radius of the circle must know the length or area. If we know one of the ukazannh values will not be difficult to calculate the radius of the circle for us.
The circle radius is calculated as follows:
Where R  radius of the circle, S  area of a circle, P  the circle length, D  diameter, π  Pi is always approximately equal to 3.14.
The radius of the circle through its length 

The radius of the circle through the area 

The radius of the circle through diameter 
