例5-3
#include<stdio.h> #include<math.h> int main(void) { double e,pi; double funpi(double e);
printf("Enter e:"); scanf("%lf",&e); pi=funpi(e); printf("pi=%f\n",pi);
return 0; }
double funpi(double e) { int denominator,flag; double item,sum;
flag=1; denominator=1; item=1.0; sum=0; while(fabs(item)>=e){ item=flag*1.0/denominator; sum=sum+item; flag=-flag; denominator=denominator+2; }
return sum*4; }