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

int main() {
    double x;
    int n;
    scanf("%lf", &x);
    printf("Enter the value of x (in radians): %lf\n",x);
    
    scanf("%d", &n);
    printf("Enter the number of terms (n):%d \n",n);
   

    double result = 1.0;
    double term = 1.0;
    int sign = -1;

    for (int i = 2; i <= n; i += 2) 
    {
        term *= (x * x) / (i * (i - 1));
        result += sign * term;
        sign *= -1;
    }

    double actualResult = cos(x);

    printf("Approximation of cos(%.2lf) using %d terms: %.6lf\n", x, n, result);
    printf("Actual cos(%.2lf) using math.h: %.6lf\n", x, actualResult);

    return 0;
}