quá dễ
uses crt;
var r:integer;
cv,dt:real;
begin
clrscr;
repeat
write('nhap ban kinh:'); readln(r);
if r<0 then writeln('nhap lai');
until r>0;
cv:=2*r*pi;
writeln('chu vi hinh tron la: ',cv:4:2);
dt:=sqr(r)*pi;
writeln('dien tich hinh tron la: ',dt:4:2);
readln;
end.
Program HINHTRON;
Uses Crt;
Var r,dt,cv:real;
Const pi=3.14;
Begin
Clrscr;
Writeln('TINH DIEN TICH HINH TRON:');
Write ('Nhap ban kinh R=');readln(r);
dt:=pi*r*r;
Writeln('Dien tich hinh tron la:',dt:6:2);
Readln;