Trace of a Matrix

Trace of a Matrix

## Definition / Concept

The trace of a square matrix is the sum of its principal diagonal elements.

For:

$$A=[a_{ij}]_{n\times n}$$

the trace is:

$$\operatorname{tr}(A)=a_{11}+a_{22}+\cdots+a_{nn}$$

## Usage

- Used in characteristic equations and matrix identities.