OK so for 1 I know it's (n-1)! (because cycle 1234 is the same as 2341) but I don't know how to prove it
for 2a) we know that if cycle has ck elements then it's sign is (-1)ck-1 and we know that sgn(a*b)=sgn(a)*sgn(b). Does the second equality mean that ? If no, how to prove it?
for 2b) we would have to prove that but I don't know how to prove it - help?