I guess you mean:
"How do you find the radius if you are given the diameter?"
You take the diameter and divide it by 2.
Divide the circumference by 2PI to find the radius. ( C = 2PI*Radius)
the radius is half the diameter
The radius is half the diameter.
Double the radius
You times the radius by 2.
divide diameter by 2 = radius
The diameter of the semicircle will be twice the radius.
The radius of a cylinder given only the height could be anything you like.
You just multiply the given radius by 2. That is diameter is just double of the radius. This is universal formula.
you have multiplythe radius by 2 to get the diameter
radius of curvature = 2Focal length
The radius of a sphere is 1/2 of its height.