Find inverse of $(1348)$ in $S_9.$
Here, we are using the cycle notation.
Clearly, the inverse is $(8431).$ Since $(1348)\circ (8431)$ will have $$8\rightarrow 4 \rightarrow 8 $$ $$4\rightarrow 3 \rightarrow 4 $$ $$3\rightarrow 1 \rightarrow 3 $$ $$1\rightarrow 8 \rightarrow 1 $$
So $(1348)\circ (8431)=e$
But we also have $(1348)\circ(1348)\circ (1348)\circ (1348)=e.$
So the inverse of $(1348)$ is $(1348)^3=(1348)\circ(1348)\circ (1348)=(8134).$
$$1\rightarrow 3 \rightarrow 4 \rightarrow 8 $$ $$3\rightarrow 4 \rightarrow 8 \rightarrow 1 $$ $$4\rightarrow 8 \rightarrow 1 \rightarrow 3 $$ $$8\rightarrow 1 \rightarrow 3 \rightarrow 4$$
Clearly $(8134)$ is not the inverse of $(1348).$ What mistake have I made?
Thanks in advance!
EDIT: I think I got the mistake, so after $(1348)^3,$ we get $$1\rightarrow 8 $$ $$3\rightarrow 1 $$ $$4\rightarrow 3 $$ $$8\rightarrow 4 $$
So, the answer is $$(1\rightarrow 8\rightarrow 4\rightarrow 3)=(1843)=(8431)$$
Here $1 \mapsto 3 \mapsto 4 \mapsto 8$ is the result of applying the permutation $3$ times.
So this means in $(1348)^3$, $1$ is mapped to $8$. Reading the others, we get $3\mapsto 1, 4\mapsto 3, 8\mapsto 4.$
If we convert that to this notation, we get $(1348)^3 = (1843),$ which is the same as $(8413).$
When you wrote $(8134)$, I think you just read the right-most numbers, which is not the right way to interpret it.