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

double fact(double x)
{
    if (!x)
        return 1;

    return (fact(x - 1) * x);
}

double sinx(double x)
{
    const unsigned int N = 50;

    double result = 0;
    unsigned int n;
    for (n = 1; n <= N; ++n)
        result += ((pow(-1, n + 1) * pow(x, 2 * n - 1))
                                    / fact(2 * n - 1));

    return result;
}

int main()
{
    double sx = sinx(0.8);
    printf("%f \n", sx);

    return 0;
}