Area of a circle

class Circle { // Declare the data members. public double diameter; public double radius; public const double PI = 3.14159; // This computes the area of a circle. public double area() { double theArea; theArea = PI * ( radius * radius ); return theArea; } // This computes the circumference of a circle. public double circumference() { double theCircumference; diameter = (radius * 2); theCircumference = PI * diameter; return theCircumference; } }

http://www.mathgoodies.com/lessons/vol2/circle_area.html

Area of circle formula: A = pi * r^2 where r is radius. Radius you can get using following formula: x2 + y2 = r2