Trace of a matrix

The trace of a square matrix is the sum of the entries on its main diagonal. It is used in linear algebra for matrix invariants, similarity checks, and as the sum of eigenvalues.

\operatorname{tr}(\mathbf{A}) = \sum_{i} A_{ii}

What the symbols mean

a square matrix
the diagonal entry in row and column i
index running over the rows (and columns) of the matrix

About this formula

  • FieldMathematics
  • TopicLinear algebra
  • LevelUniversity
  • Also calledtrace of square matrix, sum of diagonal elements, matrix trace formula, tr A, trace of matrix
  • SourceWikidata Q321102

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