Brahmagupta matrix

From Wikipedia, the free encyclopedia

The following matrix was given by Indian mathematician Brahmagupta in 628:

B(x,y) = \begin{bmatrix} x & y \\ \pm ty & \pm x \end{bmatrix}.

It satisfies

B(x_1,y_1) B(x_2,y_2) = B(x_1 x_2 \pm ty_1 y_2,x_1 y_2 \pm y_1,x_2).\,

Powers of the matrix are defined by

B^n = \begin{bmatrix} x & y \\ ty & x \end{bmatrix} = \begin{bmatrix} x_n & y_n \\ ty_n & x_n \end{bmatrix} \equiv B_n.

The \ x_n and \ y_n are called Brahmagupta polynomials. The Brahmagupta matrices can be extended to negative integers:

B^{-n} = \begin{bmatrix} x & y \\ ty & x \end{bmatrix}^{-n} = \begin{bmatrix} x_{-n} & y_{-n} \\ ty_{-n} & x_{-n} \end{bmatrix} \equiv B_{-n}.

[edit] See also

[edit] External links

Retrieved from "http://en.wikipedia.org../../../b/r/a/Brahmagupta_matrix.html"