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/******¼ÆËãÆ÷1.0 from Tony*********/
#include<stdio.h>
#include<math.h>
//ÉùÃ÷Çø
void displaymenu(); //main menu  
double add(double x,double y);  
double sub(double x,double y);  
double multi(double x,double y);
double divide(double x,double y);
int arith_compliment(int x,int y);
long int factorial(int n);
int sum_n(int n);

main()
{
 int choice;
 double tmp1,tmp2;
 double result;
 while(1)
 {
  displaymenu();
  printf("\n ÇëÑ¡ÔñÄúÐèÒªµÄ¼ÆËãÀàÐÍ£º(1,2,3,4,5,6,7,8)?\n");
  scanf("%d",&choice);


  switch(choice)
  {
  case 1:
  printf("please input two number to add:"); //¼Ó·¨
  scanf("%lf%lf",&tmp1,&tmp2);
  result=add(tmp1,tmp2);
  printf("%lf+%lf=%lf\n",tmp1,tmp2,result);
  break;
  case 2:
  printf("please input two number to sub:"); //¼õ·¨
  scanf("%lf%lf",&tmp1,&tmp2);
  result=sub(tmp1,tmp2);
  printf("%lf-%lf=%lf\n",tmp1,tmp2,result);
  break;
  case 3:
  printf("please input two number to multi:"); //³Ë·¨
  scanf("