Chapter 13, Problem 13.17E

(a) In the $T_{\text{d}}$ point group, an $S_4{}^{-1}$ improper rotation is equivalent to what other improper rotation? (b) In the $D_{6\text{h}}$ point group, the symmetry operation labeled ${\text{C}}_2{}^{-1}$ is equivalent to what other symmetry operation?