C语言,求三角形面积:从键盘输入三个顶点坐标(x1,y1)(x2,y2)(x3,y3...答:include #include float dis(float x1,float y1,float x2,float y2){float dx,dy;dx=x1-x2;dy=y1-y2;return sqrt(dx*dx+dy*dy);}int main(){float x1,x2,x3,y1,y2,y3,p,s,a,b,c;scanf("%f %f",&x1,&y1);scanf("%f %f",&x2,&y2);scanf("%f %f",&x3,&y3);a=...