9 Linear Algebra

9.1 Elementary Example

9.1.1 Simple

Linear algebra studies vectors and linear maps. Here three vectors in a plane.

\[ V = \{ e_{1},\ e_{2},\ v \} \]

\[ e_{1} = (1,0),\quad e_{2} = (0,1),\quad v = (2,3) \]

where

  • \(V\) is a set of sample vectors.
  • \(e_{1}, e_{2}\) form the standard basis of \(\mathbb{R}^{2}\).

9.1.2 General

Matrices represent linear maps. A \(3 \times 3\) matrix acts on \(\mathbb{R}^{3}\).

\[ A = \begin{pmatrix} 1 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 3 \end{pmatrix} \]

\[ A(x_{1},x_{2},x_{3}) = (x_{1},\ 2 x_{2},\ 3 x_{3}) \]

where

  • \(A\) is a linear transformation written as a matrix.