#include <iostream>
struct Point
{
double x, y;
} ;
struct Vector2D
{
double x, y;
} ;
int main( )
{
using namespace std;
cout << "假設平面上有向量AB(方向由A往B)與向量CD(方向由C往D)" << endl
<< "此2個向量都平行X軸" << endl;
Point A, B;
cout << "A 的 X 座標>" ;
cin >> A.x ;
cout << "A 的 X 座標為 " << A.x << endl;
cout << "B 的 X 座標>" ;
cin >> B.x ;
cout << "B 的 X 座標為 " << B.x << endl;
Vector2D AB = { B.x - A.x , 0 } ;
Point C, D;
cout << "C 的 X 座標>" ;
cin >> C.x ;
cout << "C 的 X 座標為 " << C.x << endl;
cout << "D 的 X 座標>" ;
cin >> D.x ;
cout << "D 的 X 座標為 " << D.x << endl;
Vector2D CD = { D.x - C.x , 0 } ;
cout << "若AB與CD方向同向,則變數a為true" << endl
<< "若AB與CD方向反向,則變數a為false" << endl;
bool a = ( CD.x * AB.x > 0 ) ;
cout << "a = " << boolalpha << a;
return 0 ;
}
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