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$A 2\times 2$ transformation matrix maps the standard basis vectors to its own columns. Specifically, the first column of the matrix is the image of the vector $[1, 0]^T$, and the second column is the image of the vector $[0, 1]^T$.

Conditions: The matrix is $2\times 2$.; Working in standard Cartesian coordinates.

Matrix subtraction is performed entrywise. Given two matrices of the same size, subtract the corresponding entry of the second matrix from the corresponding entry of the first matrix to get the result at that position.

Conditions: Both matrices must have identical dimensions.

Each column of $a 2\times 2$ matrix can be read as the coordinates of a vector in the 2D plane. For the matrix $A = \begin{bmatrix} 3 & 1 \\ 1 & 2 \end{bmatrix}$, the first column $\begin{bmatrix} 3 \\ 1 \end{bmatrix}$ represents the vector from the origin to the point (3,1), and the second column $\begin{bmatrix} 1 \\ 2 \end{bmatrix}$ represents the vector from the origin to the point (1,2).

Conditions: The matrix is $2\times 2$.; Working in standard Cartesian coordinates.

To compute the matrix for the composition $A \circ B$, apply the transformation $A$ to each column of the matrix $B$. The resulting vectors form the columns of the matrix $A \circ B$.

Conditions: A and B are both 3x3 matrices.; The operation is performed over the real numbers.; These are real linear maps with compatible input and output spaces, represented using standard column-vector coordinates.

Matrix addition is performed by adding corresponding entries. If two matrices have the same number of rows and columns, their sum is a new matrix where each element $(i,j)$ equals the sum of the elements at position $(i,j)$ in both original matrices.

Conditions: Both matrices must have identical dimensions (same $m \times n$).

The j-th column of the composed matrix $A \circ B$ is the image under A of the j-th column of B. To find a missing column, identify the corresponding column in B, treat it as an input vector, and apply the transformation A to it.

Conditions: A is a linear transformation represented by a matrix.; Columns are read as vectors in the domain of A.

The determinant is computed using the standard $2\times 2$ rule $ad - bc$. For the matrix $A = \begin{bmatrix} 3 & 1 \\ 1 & 2 \end{bmatrix}$, this means multiplying the main diagonal entries ($3 \cdot 2$) and subtracting the product of the off-diagonal entries ($1 \cdot 1$).

Conditions: The matrix is $2\times 2$.; Entries are real numbers.