Square of the radius of a circle × 3.1416 = Area.
Square of the diameter of a circle × .7854 = Area.
Square of the circumference of a circle × .07958 = Area.
Half the circumference of a circle × half its diameter = Area.
Circumference of a circle × .159155 = Radius.
Square root of the area of a circle × .56419 = Radius.
Circumference of a circle × 31831 = Diameter.
Square root of the area of a circle × 1.12839 = Diameter.
Diameter of a circle × .86 = Side of inscribed equilateral triangle.