# NAG FL Interfacef06bhf (drot2)

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## 1Purpose

f06bhf applies a real similarity rotation to a $2×2$ real symmetric matrix.

## 2Specification

Fortran Interface
 Subroutine f06bhf ( x, y, z, c, s)
 Real (Kind=nag_wp), Intent (In) :: c, s Real (Kind=nag_wp), Intent (Inout) :: x, y, z
#include <nag.h>
 void f06bhf_ (double *x, double *y, double *z, const double *c, const double *s)
The routine may be called by the names f06bhf or nagf_blas_drot2.

## 3Description

f06bhf applies a real similarity rotation, with parameters $c$ and $s$, to a given $2×2$ real symmetric matrix; that is, it performs the operation:
 $( x y y z ) ← ( c s -s c ) ( x y y z ) ( c -s s c ) .$

None.

## 5Arguments

1: $\mathbf{x}$Real (Kind=nag_wp) Input/Output
On entry: the value $x$, the $\left(1,1\right)$ element of the input matrix.
On exit: the transformed value $x$.
2: $\mathbf{y}$Real (Kind=nag_wp) Input/Output
On entry: the value $y$, the $\left(1,2\right)$ or $\left(2,1\right)$ element of the input matrix.
On exit: the transformed value $y$.
3: $\mathbf{z}$Real (Kind=nag_wp) Input/Output
On entry: the value $z$, the $\left(2,2\right)$ element of the input matrix.
On exit: the transformed value $z$.
4: $\mathbf{c}$Real (Kind=nag_wp) Input
On entry: the value $c$, the cosine of the rotation.
5: $\mathbf{s}$Real (Kind=nag_wp) Input
On entry: the value $s$, the sine of the rotation.

None.

Not applicable.