Seeking cosx values: according to the following approximation formula evaluation cosx, requires less than an absolute value accumulated until the time of 1e-6.

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

void main() {
    double x, t, s = 0;
    int i = 0;
    scanf("%lf", &x);
    t = 1;
    while (fabs(t) >= 1e-6) {
        s += t;
        i++;
        t = -t * x * x / (2 * i) / (2 * i - 1);
    }
    printf("%.2lf", s);
}