R R R R (0,-R/√2) (0,R/√2) (0,0) (R/√2,0) (-R/√2,0) x y T O O0 O1 S RRRR(0,-R/√2)(0,R/√2)(0,0)(R/√2,0)(-R/√2,0)xyTOO0O1S