C語言用公式求π近似值

終止條件: 某一項: 1 / n+2 < 10 ^ -6;

1e-6即0.000001,

代碼如下:

#include<stdio.h>
#include <math.h>

int main() {
    double quarter = 0;
    double PI = 0;
    int sign = -1;
    double term = 1.0;
    for ( ; 1.0 / term > 1e-6; ) {
        // pow(10, -6) == 1e-6
        sign = -1 * sign;
        quarter = quarter + sign * (1.0 / term);
        term = term + 2;
    }
    PI = quarter * 4;
    printf("%.14f\n" ,PI);
    return 0;
}

這里能算出精確到小數后14位,后面都是0.

結果:

3.141590653589692