Program He_Toa_Do;

Var Xa,Ya,Xb,Yb:real;

    d:integer;

Begin

repeat

Writeln('Nhap toa do diem A:');

Write('H.Do:');Readln(Xa);

Write('T.Do:');Readln(Ya);

until (Xa<>0) and (Ya<>0);

Repeat

Writeln('Nhap toa do diem B:');

Write('H.Do:');Readln(Xb);

Write('T.Do:');Readln(Yb);

until (Xb<>0) and (Yb<>0);

Writeln('a) Xet tinh chat doi xung: ');

Write('Doi xung truc tung:'); if (Ya=Yb) and (Xa=-Xb) then Writeln('CO') else Writeln('KHONG');

Write('Doi xung truc hoanh:'); if (Ya=-Yb) and (Xa=Xb) then Writeln('CO') else Writeln('KHONG');

Write('Doi xung goc toa do:'); if (Ya=-Yb) and (Xa=-Xb) then Writeln('CO') else Writeln('KHONG');

d:=0;

if Xa*Xb<0 then d:=d+1;

if Ya*Yb<0 then d:=d+1;

if (d=2) and (Ya/Yb = Xa/Xb) then d:=1;

Writeln('b) Doan thang AB cat he truc tai ',d, ' diem');

readln;

End.