浙大版《C语言程序设计（第3版）》题目集 习题5-7 使用函数求余弦函数的近似值 (15分)

#include <stdio.h>
#include <math.h>
double funcos(double e, double x);
int main()
{
    double e, x;
    scanf("%lf %lf", &e, &x);
    printf("cos(%.2f) = %.6f\n", x, funcos(e, x));
    return 0;
}
double funcos(double e, double x)
{
    int flag = -1;
    double item = 1, m = 2, sum = 1;
    double fenmu = 1, fenzi;
    while (item > e)
    {
        for (int i = 1; i <= m; i++)
        {
            fenmu = fenmu * i;
        }
        fenzi = pow(x, m);
        item = fenzi / fenmu;
        sum = sum + flag * item;
        m = m + 2;
        fenmu = 1;
        flag = -flag;
    }
    return sum;
}