问题一百三十九：函数cos()和sin()

#include <stdio.h>#include <stdlib.h>#include <math.h>#define PI 3.1415926int   factorial(int num);double COS(double x);double SIN(double x);int main(){   double x;      printf("Please enter the Angle:");      //输入要求的角度    scanf("%lf", &x);      printf("sin(x*PI/180)=%lf\n", SIN(x* PI/180));   printf("cos(x*PI/180)=%lf\n", COS(x* PI/180));      system("PAUSE");   return 0;}//The definition of the function//**factorial function        阶乘函数    int factorial(int num)  {    int sum;        sum=0;    if(num==0 || num==1)    {        sum=1;            }    else     {         sum=num*factorial(num-1);    }        return sum;}//**sin() function      sin（）函数 double SIN(double x){    int i;    int k;    double sum;             k=1;    sum=0.0;        for(i=1; pow(x, i) /factorial(i)>0.0000001; i+=2)    {          sum+=k*pow(x, i) /factorial(i);          k=-1*k;       }         return sum;}//**cos() function       cos（）函数 double COS(double x){    int i;    int k;    double sum;        k=1;    sum=0.0;        for(i=0; pow(x, i) /factorial(i) >0.0000001; i+=2)    {          sum+=k*pow(x, i)/factorial(i);          k=-1*k;             }              return sum;}