填空题

下面程序的输出结果是 【15】
#include<iostream.h>
#include<math.h>
class point
double x;
double y;
public:
point(doublea,d double B)
x=a;
y=b;
friend double distance (point a,point B) ;

double distance (point a,point B)
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
void main()
point p1(1,2);
point p2(5,2);
cout<<distance(p1,p2)<<end1;

【参考答案】

D