Prove that the determinant of $ A^{-1} = \frac{1}{det(A)} $- Linear Algebra
If I have a single matrix A that is non-singular, how can I prove the determinant of its inverse = $\frac{1}{\det(A)}$?
Prove: $$ \det(\mathbf{A^{-1}}) = \frac{1}{\mathbf{\det(A)}} $$
I know that $(A)(A^{-1}) = I$, but I am not sure what to do with that knowledge.
first of all we know that
$$\det(A \cdot B)=\det(A)\times\det(B)$$
also we know that
$$A\times A^{-1}=I$$
we know that
$$\det(A \cdot A^{-1})=\det(I)$$
or
$$\det(A)\times\det(A^{-1})=\det(I)$$
Can you continue from this? Ask yourself: what is $\det(I)$?) Take the example of the $3\times 3$ identity matrix:
$$ I = \begin{pmatrix}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{pmatrix}$$
$$ \det(I) = 1$$
So,
$$\det(A)\times\det(A^{-1})=1$$
or
$$\boxed{\det(A^{-1})=\frac{1}{\det(A)}}$$