Talk:Cofactor (linear algebra)

"Specifically the cofactor of the (i, j) entry of a matrix, also known as the (i, j) cofactor of that matrix, is the signed minor of that entry." Shouldn't this say: "... is the signed first minor of that entry" 131.122.78.108 (talk) 14:25, 4 March 2009 (UTC)

Examples of Uses
I believe this article could benefit from a few examples of the cofactor being put to practical use. I, however, do not have the knowledge to do so as I am just now learning about cofactors. Anyone willing to provide examples - mathematical or physical? --BBUCommander (talk) 23:36, 24 September 2009 (UTC)

Another expression for Cofactor Matrix
I suggest to represent an entry of Cof.Matrix in the form: $$(CofA)_{ij} = \frac{1}{(n-1)!} \epsilon_{ii_{2}i_{3}...i_n} \epsilon_{jj_2j_3...j_n} a_{i_2j_2} a_{i_3j_3} \cdots a_{i_nj_n},$$ where $$\epsilon$$ is Levi_Civita symbol, and Einstein convention of summation applies. Particularly, in the 3-dimensional case (n=3) we have: $$(CofA)_{i\alpha} = \frac{1}{2}\epsilon_{ijk} \epsilon_{\alpha\beta\gamma} a_{j\beta} a_{k\gamma}.$$

Could you please verify that and find a good reference. — Preceding unsigned comment added by 94.193.53.206 (talk) 00:16, 3 November 2011 (UTC)

Removal of "Informal approach to minors and cofactors"
I propose to remove the "Informal approach to minors and cofactors" section and leave only the "Formal definition" one. That distiction between even (i+j) and uneven (i+j) is not only useless but creates confusion in who reads. The $$(-1)^(i+j)$$ approach in the formal definition is the correct one. Raffamaiden (talk) 10:48, 22 April 2013 (UTC)


 * I agree; in fact, I just merged the entire article in Minor (linear algebra).. have a look to see if you agree with the changes. Mark M (talk) 14:35, 22 April 2013 (UTC)