计算三角形的面积和周长, 1.先设计一个POINT类,包括其构造方法设置和修改坐标,求解两点距离

class point { int x; int y; public: point (int x1=0,int y1=0) {x=x1;y=y1;}; virtual ~point() {}; void alt(int x2,int y2) { x=x2;y=y2; } void copy(point b) { x=b.x;y=b.y; } int dis(point a) {