#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a,b,c;
    printf("Please enter side A:\n");
    scanf("%d",&a);
    printf("Please enter side B:\n");
    scanf("%d",&a);
    printf("Please enter side C:\n");
    scanf("%d",&a);
        if (a<b+c)&&(b<a+c)&&(c<a+b)
        {printf("It is an triangle\n");
          if (a==b)&&(b==c) printf("Equilateral\n");
          else if (a==b)||(b==c) printf("Isosceles\n");
               else printf ("Scalene\n");
                  if (a^2==b^2+c^2)||(b^2==a^2+c^2)||(c^2==a^2+b^2) printf("Rectangle\n");


       }else printf("Not triangle\n");
    return 0;
}




顯示是if (a<b+c)&&(b<a+c)&&(c<a+b)這行有錯

不好意思，

printf("Please enter side A:\n");
    scanf("%d",&a);
    printf("Please enter side B:\n");
    scanf("%d",&a);
    printf("Please enter side C:\n");
    scanf("%d",&a);
輸入的應該分別是abc，但是我改了，還是先是錯誤在那一行

if语句是要用一个括号把整个条件表达式括住的