cos

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

double factorial(double n){
    if(n==0)
        return 1;
    return (n * factorial(n-1.0));
}

int main(){
    int i=0,flag=1;
    double cosx,term, x= (M_PI/4);
    while(i<=1000){

        term =(double) (powl(x,(double)i)/factorial((double)i));

        if(flag==1){
            cosx += term;
            flag=0;
        }else{
            cosx -= term;
            flag=1;
        }

        i += 2;
    }

    printf("cosx=>%f \ncos=>%f\n",cosx,cos(x));
    return 1;
}