Cara Membuat Perhitungan luas dan keliling lingkaran with C++

# include
# include
void main ()
{
const float phi = 3.14;
float jari_jari, luas, keliling;

cin>>jari_jari;
luas=phi*jari_jari*jari_jari;
keliling=2*phi*jari_jari;
cout<<"luas ="< BlogThis!