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Uses crt;
Var a1,b1,c2,h1,h2,d1,e,f,g,x,c1,s1,s2,s3:real;
key:char;
i,n1:byte;
Procedure A;
Begin
Repeat
clrscr;
Writeln('tinh chu vi cua 1 tam giac biet do dai 3 canh');
Writeln('---------------------------------------------');
Write('Nhap do dai canh thu 1: '); Readln(a1);
Write('Nhap do dai canh thu 2: '); Readln(b1);
Write('Nhap do dai canh thu 3: '); Readln(c2);
c1:=a1+b1+c2;
Write('Chu vi hinh tam giac do la: ',c1:3:1);
key:=readkey;
Until key='0';
End;
Procedure B;
Begin
Repeat
clrscr;
Writeln('Tinh dien tich cua 1 tam giac biet chieu cao va canh day tuong ung');
Writeln('------------------------------------------------------------------');
Write('Nhap chieu cao tam giac: '); Readln(h1);
Write('Nhap do dai canh day tuong ung: '); readln(d1);
s1:=(d1*h1)/2;
Writeln('Dien tich tam giac do la: ',s1:3:1);
key:=readkey;
Until key='0';
End;
Procedure C;
Begin
Repeat
clrscr;
Writeln('Tinh dien tich HCN biet do dai 2 canh');
Writeln('-------------------------------------');
Write('Nhap do dai cua chieu rong: '); readln(e);
Write('Nhap do dai cua chieu dai: '); readln(f);
s2:=e*f;
Writeln('Dien tich HCN do la: ',s2:3:1);
key:=readkey;
Until key='0';
End;
Procedure D;
Begin
Repeat
clrscr;
Writeln('Tinh dien tich hinh thang biet do dai 2 canh day va chieu cao');
Writeln('-------------------------------------------------------------');
Write('Nhap do dai canh day thu 1: '); readln(g);
Write('Nhap do dai canh day thu 2: '); readln(x);
Write('Nhap chieu cao: '); readln(h2);
s3:=(g+x)*h2/2;
Writeln('Dien tich hinh thang la: ',s3:3:1);
key:=readkey;
Until key='0';
End;
Procedure Trang_chu;
Begin
a1:=0;b1:=0;c2:=0;h1:=0;h2:=0;d1:=0;e:=0;f:=0;g:=0;x:=0;c1:=0;s1:=0;s2:=0;s3:=0;
clrscr;
Writeln('A: Tinh chu vi cua 1 tam giac biet do dai 3 canh');
Writeln('B: Tinh dien tich cua 1 tam giac biet chieu cao va canh day tuong ung');
Writeln('C: Tinh dien tich HCN biet do dai 2 canh');
Writeln('D: Tinh dien tich hinh thang biet do dai 2 canh day va chieu cao');
Writeln('0: Thoat chuong trinh');
Writeln;
Write('Nhap chu cai tuong trung: '); key:=readkey;
Case key of 
'A':A; 
'B':B;
'C':C;
'D':D;
'0':exit;
else
Begin
writeln('Cong thuc khong ton tai');
Delay(1500);
End; 
End;
Trang_chu;
End;
BEGIN
Trang_chu;
END.