Editing Linear form (section)

=== Trace of a square matrix ===
The [[Trace (linear algebra)|trace]] <math>\operatorname{tr} (A)</math> of a square matrix <math>A</math> is the sum of all elements on its [[main diagonal]]. Matrices can be multiplied by scalars and two matrices of the same dimension can be added together; these operations make a [[vector space]] from the set of all <math>n \times n</math> matrices. The trace is a linear functional on this space because <math>\operatorname{tr} (s A) = s \operatorname{tr} (A)</math> and <math>\operatorname{tr} (A + B) = \operatorname{tr} (A) + \operatorname{tr} (B)</math> for all scalars <math>s</math> and all <math>n \times n</math> matrices <math>A \text{ and } B.</math>