设R={,,},试求r(R),s(R)和t(R).

r(R)=R ∪ Ix= { ,,,,,}s(R)=R ∪ R(逆)= { ,,,,,}s(R)=R(1阶) ∪ R(2阶)∪ R(3阶)...= { ,,,,,}R(1阶)= R= { ,,}R(2阶)= { ,,}R(3阶)= { ,,}R(4阶)= { ,,}故：s(R)= { ,,,,,,,,}有些符号鉴于难打 就用中文代替了....