In ⁠ D 4 ⁠, the group of symmetries of a square, with its subgroup R of rotations, the left cosets g R are either equal to ⁠ R ⁠, if g is an element of R itself, or otherwise equal to U = f c R = { f c , f d , f v , f h } (highlighted in green in the Cayley table of ⁠ D 4 ⁠). The subgroup R is normal, because f c R = U = R f c and similarly for the other elements of the group. (In fact, in the case of ⁠ D 4 ⁠, the cosets generated by reflections are all equal: ⁠ f h R = f v R = f d R = f c R ⁠.)