generators: s1=(57)(68) s2=(56)(78) s3=(34) s4=(37)(48) s5=(26)(48) s6=(24)(68) s7=(78) s8=(68) s9=(48) S={si : i=1~9} <S> means a permutation group generate by S give a=(2345678) (1) is a in <S>??? (2) a=?? (please give power of generator to represent a ;for example we can represent (24)=s6*s8) And more general problem given a permutation group <S> by its generator set S={a,b,c,...} the elements of S has the type like (12);(1324); (13)(24)...etc. if we give a element p which is in the type like the elements in S Is there an algorithm to distinguish whether p in <S>?? and is there an algorithm to write p = the power of the generators ?? Is there som book which had metion some theory about this?? ----------------------------------------------------------------- ¨C¤Ñ³£ Yahoo!©_¼¯ ®üªºÃC¦â¡B·ªº®ð®§¡B·R§Aªº·Å«×¡AºÉ¦b«H¯È©³¹Ï http://tw.promo.yahoo.com/mail_premium/stationery.html