03_001_Transpose_matrix_Squre_matrix_Diagonal_matrix_Scalar_matrix_Identity_matrix_Symmetry_matrix_Orthogonal_matrix.html ========================================================= transpose matrix 2018-06-11 07-53-43.png squre matrix diagonal matrix 2018-06-11 07-54-55.png scalar matrix 2018-06-11 07-55-25.png identity matrix 2018-06-11 07-56-24.png symmetry matrix 2018-06-11 07-56-55.png $$$S^{T}=S$$$ orthogonal matrix 2018-06-11 08-05-14.png $$$AA^{T}=A^{T}A=I$$$ Let's think of matrix A which is composed of n number of row vectors $$$x_{1}, x_{2}, ..., x_{n}$$$ 2018-06-11 07-58-57.png $$$(x_{1},x_{1})=x_{1}\cdot x_{1}$$$ $$$0 = x_{1}\cdot x_{2} \rightarrow \cos\theta=0$$$, $$$\theta=90^{\circ}$$$ oneself$$$\cdot$$$ oneself = 1, oneself$$$\cdot$$$ other = 0 In other words, vectors $$$x_{1}, x_{2}, ..., x_{n}$$$ are orthogonal