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;
}