/* This program reports average area of circle using functions */ #include<stdio.h> #include<math.h> #define PI 3.1415926 double average(double, double) ; double circleArea(double) ; int main() { double outerDiameter, innerDiameter ; double avgArea ; printf("Outer Diameter = ") ; scanf("%lf", &outerDiameter) ; printf("Inner Diameter = ") ; scanf("%lf", &innerDiameter) ; avgArea = average(circleArea(innerDiameter), circleArea(outerDiameter) ) ; printf("Average Area = %f\n", avgArea) ; return 0 ; } /* Calculate the average. */ double average(double value1, double value2) { double avgValue ; avgValue = (value1 + value2) / 2.0 ; return avgValue ; } /* Calculate the area of a circle. */ double circleArea (double diameter) { double area, radius ; radius = diameter / 2.0 ; area = PI * radius * radius ; // printf("diameter = %f, radius = %f and area = %f\n", // diameter, radius, area) ; return area ; }