#循环语句中给变量赋值的表达式不能循环 #这个是代码，然后它是求三角形面积的

#include<stdio.h>
#include<math.h>
int main()
{
    double x1,y1,x2,y2,x3,y3;
    double a,b,c,p,s,i,A,B,C;
    printf("please input x1,y1,x2,y2,x3,y3:\n");
    scanf("x1,y1,x2,y2,x3,y3",&x1,&y1,&x2,&y2,&x3,&y3);
    for(i=1;i<=100;i++)
    {  
    A=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
    B=(x1-x3)*(x1-x3)+(y1-y3)*(y1-y3);
    C=(x3-x2)*(x3-x2)+(y3-y2)*(y3-y2);
    a=sqrt(A);
    b=sqrt(B);
    c=sqrt(C); 
    p=(a+b+c)/2;
    if(a+b>c&&a-b<c&&a+c>b&&a-c<b&&b+c>a&&b-c<a)
    {
    s=sqrt(p*(p-a)*(p-b)*(p-c));
    printf("s=%lf\n",s);
    }
    else
    printf("三角形不成立\n"); 
    scanf("x1,y1,x2,y2,x3,y3",&x1,&y1,&x2,&y2,&x3,&y3);
    }
    return 0;
}

scanf("%lf%lf%lf%lf%lf%lf",......
输入空格间隔的六个坐标值