程序代码：

#include <stdio.h>

int main( void )
{
    double x;
    unsigned n;
    scanf( "%lf %d", &x, &n );
    {
        double result = x;
        double temp = x;
        unsigned i;
        for( i=1; i<n; ++i )
        {
            temp *= -x*x/(4*i*i+2*i);
            result += temp;
        }

        printf ("%.8f\n", result );
    }
    return 0;
}