VG1
ordbok
Dictionary: Diameter and radius
Radius is the distance from the centre to the edge of a circle. Diameter is the distance all the way across — twice the radius.
d = 2r · r = d/2
Radius (r) is measured from the centre to the edge. Diameter (d) is the longest line through the circle.
Area = π · r² · Circumference = 2 · π · r
The circle is the most perfect shape.
— Proclus (412–485)