# dlartg.f man page

dlartg.f —

## Synopsis

### Functions/Subroutines

subroutinedlartg(F, G, CS, SN, R)DLARTGgenerates a plane rotation with real cosine and real sine.

## Function/Subroutine Documentation

### subroutine dlartg (double precisionF, double precisionG, double precisionCS, double precisionSN, double precisionR)

**DLARTG** generates a plane rotation with real cosine and real sine.

**Purpose:**

```
DLARTG generate a plane rotation so that
[ CS SN ] . [ F ] = [ R ] where CS**2 + SN**2 = 1.
[ -SN CS ] [ G ] [ 0 ]
This is a slower, more accurate version of the BLAS1 routine DROTG,
with the following other differences:
F and G are unchanged on return.
If G=0, then CS=1 and SN=0.
If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any
floating point operations (saves work in DBDSQR when
there are zeros on the diagonal).
If F exceeds G in magnitude, CS will be positive.
```

**Parameters:**

*F*

```
F is DOUBLE PRECISION
The first component of vector to be rotated.
```

*G*

```
G is DOUBLE PRECISION
The second component of vector to be rotated.
```

*CS*

```
CS is DOUBLE PRECISION
The cosine of the rotation.
```

*SN*

```
SN is DOUBLE PRECISION
The sine of the rotation.
```

*R*

```
R is DOUBLE PRECISION
The nonzero component of the rotated vector.
This version has a few statements commented out for thread safety
(machine parameters are computed on each entry). 10 feb 03, SJH.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 98 of file dlartg.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlartg(3) is an alias of dlartg.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK