cách 1: xài bán kính
uses crt;
var r,s,vc: real;
begin
clrscr;
write ('nhap ban kinh: '); readln (r);
cv:=r*2*Pi;
s:=r*r*Pi;
Writeln ('chu vi la: ',cv:1:2);
writeln ('dien tich la: ',s:1:2);
readln;
end.
cách 2: xài đường kính
uses crt;
var d,s,vc: real;
begin
clrscr;
write ('nhap ban kinh: '); readln (d);
cv:=d*Pi;
s:=(d/2)*(d/2)*Pi;
Writeln ('chu vi la: ',cv:1:2);
writeln ('dien tich la: ',s:1:2);
readln;
end.