Math Help - Matrix operation

1. Matrix operation

Determine A^18

dont know what to do besides to just count. But i had a similar question before where i could se it was a rotation matrix and then it was easy. Is there an easy way for this one to?

Thanks!

2. Decompose

$A=2I+N$

and apply the Newton's binomial theorem. The matrix N is nilpotent of order 3.