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;

}