[Math] Permutations and disjoint cycles

permutations

Write the following permutation as product of disjoint cycles

$$(12)(13)(14)(15)$$

Could someone explain how to proceed with this question ? I have four more similar, so I just want somebody to solve this one so that I can have a basic example.

Thank you in advance

Best Answer

We write this permutation on its standard form $$\sigma=\left(\begin{array}\\ 1&2&3&4&5\\ 5&1&2&3&4 \end{array}\right)$$ and this a cycle since $$1\overset \sigma\rightarrow5\overset \sigma\rightarrow4\overset \sigma\rightarrow3\overset \sigma\rightarrow2\overset \sigma\rightarrow1$$ so $$\sigma=(1\ 5\ 4\ 3\ 2)$$