# Tagged: matrix exponential of a diagonal matrix

## Problem 681

For a square matrix $M$, its matrix exponential is defined by
$e^M = \sum_{i=0}^\infty \frac{M^k}{k!}.$

Suppose that $M$ is a diagonal matrix
$M = \begin{bmatrix} m_{1 1} & 0 & 0 & \cdots & 0 \\ 0 & m_{2 2} & 0 & \cdots & 0 \\ 0 & 0 & m_{3 3} & \cdots & 0 \\ \vdots & \vdots & \vdots & \vdots & \vdots \\ 0 & 0 & 0 & \cdots & m_{n n} \end{bmatrix}.$

Find the matrix exponential $e^M$.