习题5-7 使用函数求余弦函数的近似值

 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 double funcos(double e, double x);
 5 
 6 int main()
 7 {
 8     double e, x;
 9 
10     scanf_s("%lf %lf", &e, &x);
11     printf("cos(%.2f) = %.6f\n", x, funcos(e, x));
12 
13     return 0;
14 }
15 
16 double funcos(double e, double x)
17 {
18     double item = 1;
19     double numerator;        //分子
20     double denominator;    //分母
21     double result = 0;
22     int i = 0;
23     double flag = 1.0;
24 
25     while (fabs(item) > e)
26     {
27         numerator = 1;
28         for (int j = 1; j <= i; j++)
29         {
30             numerator = numerator * x;
31         }
32 
33         denominator = 1;
34         for (int k = 1; k <= i; k++)
35         {
36             denominator = denominator * k;
37         }
38 
39         item = flag * numerator / denominator;
40 
41         result = result + item;
42 
43         flag = -flag;
44 
45         i = i + 2;
46     }
47 
48     return result;
49 
50 }