问答题

下面程序用来求直角三角形斜边长度。
#include ＜iostream.h＞
#include ＜math.h＞
class Point
{ private:
double x, y;
______
public:
Point (double i = 0, double j = 0)
{x=i; y=j; }
Point( Point &p)
{x=p.x; y=p.y;}
};
class Line
{ private:
Point p1, p2;
public:
Line(Point &xp1, Point &xp2):______{}
double GetLength();
};
double Line::GetLength()
{ double dx=p2.x-p1.x;
double dy=p2.y-p1.y;
return sqrt( dx * dx + dy * dy);
}
void main()
{ Point p1, p2(6, 8);
Line L1 (p1, p2);
cout＜＜L1. GetLength()＜＜endl;
}