How to find the radius of the circle

The word radius radius translates from Latin as "spoke wheels, ray." A radius is any line segment that connects the center of a circle or sphere with any point lying on this circle or on the surface of this sphere, and also the length of this segment is the radiusom. To denote the radiusand the computing and mathematical expressions using the Latin letter R.

Instruction

1. The diameter of a circle is a line segment that passes through the center of the circle and connects two most distant between a point lying on the circumference. The length of this segment is also called a diameter of the circle. The radius is half the diameter of a circle, so if you know the diameter of this circleto find its radius by dividing it in half. R = D/2 where D is the diameter of the circle.
2. The length of the curve, forming a circle on a plane is the length of the circumference. If the known length of a circle you can use the formula: R = L/2?, where L is the length of the circle, ? is a constant equal 3,14159... Constant ? equal to the ratio of the length of the circumference to the diameter, this value is the same for all circles.
3. A circle is a geometric figure that represents the portion of the plane bounded curve is a circle. If you know the area of a circle, find the radius of a circle from the following formula: R = v(S/?), where v is the square root, S – the area of a circle.