TITLE: Finding the 10th root of a matrix
QUESTION [12 upvotes]: I want to find a $2 \times 2$ matrix, named $A$ in this situation, such that:
$$A^{10}=\begin {bmatrix} 1 & 1 \\ 0 & 1 \end {bmatrix} $$
How can I get started? I was thinking about filling $A$ with arbitrary values $a, b, c, d$ and then multiplying it by itself ten times, then setting those values equal to the given values but I quickly realized that would take too long. Is there a more efficient way?

REPLY [2 votes]: Hint: Another approach is to note that
$$
\exp\left(\begin{bmatrix}0&x\\0&0\end{bmatrix}\right)=\begin{bmatrix}1&x\\0&1\end{bmatrix}
$$