The square root of 4. In this equation C represents the circumference of the circle and d represents its diameter. Memorize the formulas of all circle concepts by using the list of various properties of circle formulae provided over here.
If the radius of a circle is extended further and touches the boundary of the circle it becomes the diameter of a circle.
Diameter Cp Note. If the radius of a circle equals 2 meters multiply it by 2 to get the diameter. C p d. A p r 2.