08/11/10 16:45:16
>>530
こんなんでいい？
#include <stdio.h>
#include <math.h>
int main (void)
{
int i;
double pi, sum, eps;
sum = 0.0;
for(i=0; i<=100; i++){
pi = 4.0 * (sum += pow(-1, i) / (2*i + 1) * (pow(0.5, 2*i+1) + pow(3, -2*i-1)));
}
printf("π≒%.8f\n", pi);
printf("ε：");
scanf("%lf", &eps);
i = 1; sum = 0.0;
while(fabs(pi*pi/6 - (sum += pow(i, -2))) >= eps)
i++;
printf("N = %d\n", i);
return(0);
}