/*tinh cosx*/

#include<stdio.h>

#include<conio.h>

#include<math.h>

double giaithua(int n)

{

    if(n==0)return 1;

    else

    return(n*giaithua(n-1));

}

int main()

{

    float x,b,s=0;

    float ts,ms,a=0.00001;

    printf("nhap x:");scanf("%f",&x);

    ts=1;

    int t=1,i=0;

    do

    {

         ms=giaithua(i);

         b=ts/ms;

         s=s+b*t;

         ts=ts*pow(x,2);

         i=i+2;

         t=(-1)*t;

    }while(b>=a);

    printf("cos %f = %f",x,s);

    getch();

    return 0;

}