C语言伤脑筋，仔细阅读题目

#include<stdio.h>
int main()
{
    int i;
    double Zi,mu,t,sum;
    i = 1;
    Zi = 1;
    mu = 1;
    sum = 0.00000000;
    t = Zi/mu;
    do 
    {
        sum += t;
        Zi *= i;
        mu *= (2*i+1);
        t = Zi/mu;
        i++;
    } while (t >= 0.00000001);
    sum *=2;
    printf("PAI的近似值是：%.8lf",sum);
    return 0;
}