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Let's say we have an invertible matrix $A$ and both $A$ and $A^{-1}$ members are whole numbers.

is it always true that $\det A = \det A^{-1}$?

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    what is $A^\prime$? The inverse of $A$? This is usually denoted $A^{-1}$. And for invertible matrices you always have $\det(A)= 1/\det(A^{-1})$.2011-12-07
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    see the question [Integer Matrices with Inverse Integer Matrix](http://math.stackexchange.com/questions/19528/integer-matrices-with-inverse-integer-matrix) and http://en.wikipedia.org/wiki/Unimodular_matrix2011-12-07
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    I presume $A'$ is the transpose of $A$. In that case the answer is yes.2011-12-07
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    uhmm -- yes. But you do not need to assume anything about $A$ in this case (like being invertible, having integer coefficients,...), do you?2011-12-07
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    Yeah i ment A' as the invers of A2011-12-07

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