Tính S(n) = 1 + x^2/2! + x^4/4! + … + x^2n/(2n)!

#include<stdio.h>
#include<conio.h>
#include<math.h>
int main()
{
	int i, n;
	float x, S, T;
	long M, N;
	printf("\nNhap x: ");
	scanf("%f", &x);
	do
	{
	printf("\nNhap n(n >= 0) : ");
	scanf("%d", &n);
	  if(n < 0)
	  {
		  printf("\n N phai >= 0. Xin nhap lai !");
	  }

	}while(n < 0);

	S = 1;
	N = 1;
	i = 1;

	while(i <= n)
	{
		T = pow(x, (2 * i ));
		M = i * 2;
		N = N * M * (M - 1);
		S = S + T/N;
		i++;
	}
	printf("\nTong la %f", S);
	getch();
	return 0;
}