“21天好习惯”第一期－16

#include
#include
int main()
{
    double x, a, s;
    int n = 1;
    scanf("%lf", &x);
    a = x;
    s = a;
    while (fabs(a) >= 1e-5)
    {
        a = -a * x * x / ((n + 1) * (n + 2));//第n项
        s = s + a;
        n += 2;
    }
    printf("%.4f", s);
    return 0;
}