Question

If A is nonsingular, then (AT )-1 =(A-1) T . (a) Verify this theorem for 2 × 2 matrices

Answer 1

Answer:

Verified

Step-by-step explanation:

Let the 2x2 matrix A be in the form of:

$\left[\begin{array}{cc}a&b\\c&d\end{array}\right]$

Where det(A) = ad - bc # 0 so A is nonsingular:

Then the transposed version of A is

$A^T = \left[\begin{array}{cc}a&c\\b&d\end{array}\right]$

Then the inverted version of transposed A is

$(A^T)^{-1} = \frac{1}{ad - cb} \left[\begin{array}{cc}a&-c\\-b&d\end{array}\right]$

The inverted version of A is:

$A^{-1} = \frac{1}{ad - bc}\left[\begin{array}{cc}a&-b\\-c&d\end{array}\right]$

The transposed version of inverted A is:

$(A^{-1})^T = \frac{1}{ad - bc}\left[\begin{array}{cc}a&-c\\-b&d\end{array}\right]$

We can see that

$(A^T)^{-1} = (A^{-1})^T$

So this theorem is true for 2 x 2 matrices