[Math] Given transformation matrix, what is the area of the resulting figure

linear algebralinear-transformationsmatrices

Given transformation matrix $$T=\begin{bmatrix}10&4\\3&8\end{bmatrix}$$
Applied to the points A(4,2) B(4,6) C(10,2) D(10,6) calculate the area of the resaulting figure.
So far I applied the transformation matrix to the given points:
\begin{bmatrix}10&4\\3&8\end{bmatrix}.\begin{bmatrix}4&4&10&10\\2&6&2&6\end{bmatrix} = \begin{bmatrix}48&64&108&124\\28&60&46&78\end{bmatrix} and the area before apllying transformation mtrix is 6×4=24 but I do not have any clue how to calculate the area after applying the transformation matrix, so, please help me and explain to me step by step how to find it.

Best Answer

The determinant scales area by $|\det(T)|$, so you may just calculate the area of the figure in the domain.

The original figure is a rectangle with area $4(6)=24$. Your determinant is $68$. So the area of the resulting figure is $$ 68(24)=1632 $$