#include <stdio.h>

#include <conio.h>

#include <math.h>

double giaithua(double n)

{

double i, ketqua=1;

for (i=2; i<=n; i++)

ketqua *= i;

return ketqua;

}

void main()

{

double ketqua, epsilon, x, n = 1,c;

printf("

Nhap gia tri x (radian) : ");

scanf("%lf", &x);

printf("

Nhap vao so c:");

scanf("%lf",&c);

ketqua=1;

do {

epsilon = pow(x, 2*n) / giaithua(2*n);

ketqua += pow(-1, n) * epsilon;

n++;

} while (fabs(epsilon) > c);

printf("

Ket qua tinh theo cong thuc = %10.8lf",ketqua);

printf("

Ket qua tinh theo ham = %10.8lf", cos(x));

getch();

}

Cach 2

#include<stdio.h>

#include<conio.h>

#include<math.h>

void main()

{

clrscr();

double t;

float a,x,cos;

printf("Nhap goc x (tinh theo do):");

scanf("%f",&x);

a=x;

x=M_PI*x/180;

cos=1;

n=1;

t=1;

do

{

t=-t*x*x/n/(n+1);

cos=cos+t;

n=n+2;

}

while (fabs(t)>0.000001);

printf("Ket qua: COS(%.2f)= %f",a,cos);

getch();

}