a = float(input("Nhap a : "))
b = float(input("Nhap b : "))
c = float(input("Nhap c : "))
if a+b>c and a+c>b and b+c>a:
    if a==b or a==c or b==c:
        if a==c==b:
            print("Day la ba canh cua tam giac deu")
        else:
            print("Day la ba canh cua tam giac can")
    elif (a**2)+(b**2)==c**2 or (a**2)+(c**2)==b**2 or (c**2)+(b**2)==a**2:
        print("Day la ba canh cua tam giac vuong")
    else:
        pass
else:
    print("Day khong phai ba canh cua tam giac")

PROGRAM DIEN TICH TAM GIAC;
{Nhap vao do dai 3 canh tam giac. Tinh dien tich tam giac ay}
VAR a,b,c,p,S:real;kt:boolean;{kt: kiem tra}
BEGIN
Write('Nhap a: ');readln(a);
Write('Nhap b: ');readln(b);
Write('Nhap c: ');readln(c);
Writeln;
kt:=(a>0)and(b>0)and(c>0)and(a+b>c)
and(b+c>a)and(a+c>b);
If kt=true then
begin
p:=(a+b+c)/2;
S:=sqrt(p*(p-a)*(p-b)*(p-c));
writeln('Dien tich S= ',S:6:2);
end
Else writeln(,'Khong thuc hien vi day khong la do dai 3 canh tam giac');
Readln
END.

* Xin chú ý với bạn rằng: Trước khi tính diện tích tam giác, ta phải kiểm tra xem ba độ dài a, b, c có phải là ba cạnh của tam giác hay không, cho nên cần phải có biến kt:boolean;{kt: kiem tra}

kt:=(a>0)and(b>0)and(c>0)and(a+b>c)
and(b+c>a)and(a+c>b)

Chúc bạn học tốt!

uses crt;
var a,b,c: real;
begin
clrscr;
write('Nhap 3 so a, b, c:');readln(a,b,c);
if (a+b>c)and(a+c>b)and(b+c>a) then
write('3 canh vua nhap la tam giac')

write('3 canh vua nhap ko phai la tam giac');
readln;
end.

var a,b,c,s,p: real;

begin

write('Nhap canh thu nhat: '); readln(a);

write('Nhap canh thu hai: '); readln(b);

write('Nhap canh thu ba: '); readln(c);

if (a+b>c) and (b+c>a) and (c+a>b) then 

begin

p:=(a+b+c)/2;

s:=sqrt(p*(p-a)*(p-b)*(p-c));

writeln('Chu vi tam giac la ',2*p:5:2, '(dvdd)');

writeln('Dien tich tam giac la: ',s:5:2, '(dvdt)');

if (a=b) and (b=c) then writeln('Day con la tam giac deu') else

if (a=b) or (b=c) or (c=a) then writeln('Day la tam giac can') else

if (a*a+b*b=c*c) or (b*b+c*c=a*a) or (c*c+a*a=b*b) then writeln('Day la tam giac vuong') else

writeln('Day la tam giac thuong');

if ((a=b) or (b=c) or (c=a)) and ((a*a+b*b=c*c) or (b*b+c*c=a*a) or (c*c+a*a=b*b)) then writeln('Day la tam giac vuong can')

end

else writeln(a:5:2,',',b:5:2,',',c:5:2,' khong la do dai mot tam giac');

end.

help me !!!!!!

uses crt;

var a,b,c:real;

begin

clrscr;

repeat

write('Nhap a='); readln(a);

write('Nhap b='); readln(b);

write('Nhap c='); readln(c);

until (a>0) and (b>0) and (c>0);

if (a+b>c) and (a+c>b) and (b+c>a) then 

begin

writeln('La do dai ba canh cua tam giac');

writeln('Chu vi tam giac la: ',a+b+c:4:2);

end

else writeln('Khong phai la do dai 3 canh cua tam giac');

readln;

end.

uses crt;

var a,b,c:real;

begin

clrscr;

repeat

write('Nhap a='); readln(a);

write('Nhap b='); readln(b);

write('Nhap c='); readln(c);

until (a>0) and (b>0) and (c>0);

if (a+b>c) and (b+c>a) and (a+c>b) then 

begin

if sqr(a)=sqr(b)+sqr(c) then writeln('Vuong')

else if sqr(b)=sqr(a)+sqr(c) then writeln('Vuong')

else if sqr(c)=sqr(a)+sqr(b) then writeln('Vuong')

else writeln('La tam giac khong vuong');

end

else writeln('Khong la ba canh trong mot tam giac');

readln;

end.

#include <iostream>
using namespace std;
int main()
{
    int a,b,c,kt;
    cout<<"Nhap a=";
    cin>>a;
    cout<<"Nhap b=";
    cin>>b;
    cout<<"Nhap c=";
    cin>>c;
    if ((a>0) and (b>0) and (c>0) and (a+b>c) and (a+c>b) and (b+c>a))
    {
        kt=0;
        if (a*a==b*b+c*c) kt=1;
        if (b*b==a*a+c*c) kt=1;
        if (c*c==a*a+b*b) kt=1;
        if ((a==b) and ((a<c) or (a>c)) and ((b<c) or (b>c))) kt=2;
        if ((b==c) and ((b<a) or (b>a)) and ((c<a) or (c>a))) kt=2;
        if ((c==a) and ((c<b) or (c>b)) and ((a<b) or (a>b))) kt=2;
        if ((a==c) and (b==c)) kt=3;
        if (kt==2) cout<<"Day la tam giac can";

else cout<<"Day khong la tam giac can";
    }
    else cout<<"Day khong la ba canh trong mot tam giac";
    return 0;
}