Wednesday, February 7, 2018

linear algebra - Determinant of ntimesn matrix - two diagonals and a corner

Suppose we have matrix which has zeroes everywhere with the exception of bottom left corner, main diagonal and right above the main diagonal
An=(b1c10000b2c20000b3bn2cn2000bn1cn1cn000bn)



If we look at Leibniz formula for determinants, we can see that there only two permutations where we have no zereos. (Namely the identity permutation and shift by one place.) From this we get for the determinant:
Dn=det(An)=b1b2bn+(1)n1c1c2cn


This is also the solution given in this question: How to find the determinant of this matrix



Are there some other interesting ways to derive this expression for the determinant?

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