<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> In linear algebra, the trace of an n - by - n square matrix A is defined to be the sum of the elements on the main diagonal (the diagonal from the upper left to the lower right) of A, i.e., </P> <Dl> <Dd> tr ⁡ (A) = ∑ i = 1 n a i i = a 11 + a 22 + ⋯ + a n n (\ displaystyle \ operatorname (tr) (A) = \ sum _ (i = 1) ^ (n) a_ (ii) = a_ (11) + a_ (22) + \ dots + a_ (nn)) </Dd> </Dl>

What is the trace of a square matrix
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