利用C语言编写公式计算π=4(1-1/3+1/5-1/7+1/9-...)的近似值，直到括号中最后一项的绝对值小于0.000001为止

#include <stdio.h>

int main() {
    double pi = 0.0, term = 1.0;
    int sign = 1, i = 1;
    while (term >= 0.000001) {
        pi += sign * term;
        sign = -sign;
        i += 2;
        term = 1.0 / i;
    }
    pi *= 4;
    printf("π的近似值为：%.6f\n", pi);
    return 0;
}