Diameter is the segment connecting two arbitrary points on the circle and passing through its center. Therefore, if the diameter you need to find by knowing the radius of the given circle, multiply the numerical value of the radius by two, and measure the value found in the same units as the radius. Example: the Radius of a circle 4 centimeters. To find the diameter of this circle. Solution: the Diameter is 4 cm*2=8 cm Answer: 8 inches.
If the diameter of the need to find through the length of the circle, then we must act using the first step. There is a formula to calculate the length of a circle: l=2PR, where l is the length of the circumference, 2 is a constant, n is the number equal to 3.14; R is the radius of the circle. Knowing that the diameter is double the radius, the above formula can be written as: l=пD, where D is the diameter.
To Express this formula diameter of circle: D=l/n, And substitute into it the known values, calculate a linear equation with one unknown. Example: to Find the diameter of a circleif its length is 3 meters. Solution: the diameter is equal to 3/3 = 1 m. Answer: the diameter equal to one meter.