Driver function
int main ( ) { float R = 30 ; cout << " Focal ▁ length ▁ of ▁ spherical " << " concave ▁ mirror ▁ is ▁ : ▁ " << focal_length_concave ( R ) << " ▁ units STRNEWLINE " ; cout << " Focal ▁ length ▁ of ▁ spherical " << " convex ▁ mirror ▁ is ▁ : ▁ " << focal_length_convex ( R ) << " ▁ units " ; return 0 ; }