naginterfaces.library.blas.drot2

naginterfaces.library.blas.drot2(x, y, z, c, s)

drot2 applies a real similarity rotation to a $2\times 2$ real symmetric matrix.

For full information please refer to the NAG Library document for f06bh

https://support.nag.com/numeric/nl/nagdoc_30/flhtml/f06/f06bhf.html

Parameters

xfloat

The value $x$, the $(1,1)$ element of the input matrix.

yfloat

The value $y$, the $(1,2)$ or $(2,1)$ element of the input matrix.

zfloat

The value $z$, the $(2,2)$ element of the input matrix.

cfloat

The value $c$, the cosine of the rotation.

sfloat

The value $s$, the sine of the rotation.

Returns

xfloat

The transformed value $x$.

yfloat

The transformed value $y$.

zfloat

The transformed value $z$.

Notes

No equivalent traditional C interface for this routine exists in the NAG Library.

drot2 applies a real similarity rotation, with parameters $c$ and $s$, to a given $2\times 2$ real symmetric matrix; that is, it performs the operation:

$$\begin{array}{c}\left(\begin{array}{cc}x& y\\ y& z\end{array}\right)\leftarrow \left(\begin{array}{cc}c& s\\ -s& c\end{array}\right)\left(\begin{array}{cc}x& y\\ y& z\end{array}\right)\left(\begin{array}{cc}c& -s\\ s& c\end{array}\right)\text{.}\end{array}$$