text: printing points based on 4 - way symmetry
code: printf ( " ( % f , ▁ % f ) STRNEWLINE " , x + xc , y + yc ) ; printf ( " ( % f , ▁ % f ) STRNEWLINE " , - x + xc , y + yc ) ; printf ( " ( % f , ▁ % f ) STRNEWLINE " , x + xc , - y + yc ) ; printf ( " ( % f , ▁ % f ) STRNEWLINE " , - x + xc , - y + yc ) ;