The answer depends on the formula for what: the radius, circumference, length of an arc, area, area of sector, area of segment: each one has a different formula.
divide diameter by 2
C=Pi x diameter
(pi)D
diameter = circumference/pi (pi = 3.14159265 or 3.14 for rough approximation).
That depends what shape you are talking about.
If you are given the radius of the circle, you can use the formula: diameter = 2*radius If you are given the circumference of the circle, you can use the formula: diameter = circumference/pi
divide diameter by 2
C=Pi x diameter
Circumference = (diameter) multiplied by (pi)
Circumference of a circle = (pi) x (diameter)
To find the diameter of a circle when given the circumference, you can use the formula: circumference = π * diameter. Given a circumference of 84 units, you can plug this value into the formula and solve for the diameter. Dividing 84 by π gives you approximately 26.67 units as the diameter of the circle.
Radius is half of the diameter, so you can easily come up with a formula: L = 0.25 * pi * d2
(pi)D
in place of r (radius) write d/2 where d is diameter
Circumfrence=diameter X 3.14 (diameter=2 X radius)
diameter = circumference/pi (pi = 3.14159265 or 3.14 for rough approximation).
You just multiply the given radius by 2. That is diameter is just double of the radius. This is universal formula.