[001A]において、\(\mathord {\textnormal {\textsf {dist}}}^{-1}(C)\circ \mathord {\textnormal {\textsf {dist}}}(C)\equiv \mathord {\textnormal {\textsf {id}}}\)と\(\mathord {\textnormal {\textsf {dist}}}(C)\circ \mathord {\textnormal {\textsf {dist}}}^{-1}(C)\equiv \mathord {\textnormal {\textsf {id}}}\)を確かめよ。