rx.c

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#include "erfa.h"

void eraRx(double phi, double r[3][3])
/*
**  - - - - - -
**   e r a R x
**  - - - - - -
**
**  Rotate an r-matrix about the x-axis.
**
**  Given:
**     phi    double          angle (radians)
**
**  Given and returned:
**     r      double[3][3]    r-matrix, rotated
**
**  Notes:
**
**  1) Calling this function with positive phi incorporates in the
**     supplied r-matrix r an additional rotation, about the x-axis,
**     anticlockwise as seen looking towards the origin from positive x.
**
**  2) The additional rotation can be represented by this matrix:
**
**         (  1        0            0      )
**         (                               )
**         (  0   + cos(phi)   + sin(phi)  )
**         (                               )
**         (  0   - sin(phi)   + cos(phi)  )
**
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
   double s, c, a10, a11, a12, a20, a21, a22;

   s = sin(phi);
   c = cos(phi);

   a10 =   c*r[1][0] + s*r[2][0];
   a11 =   c*r[1][1] + s*r[2][1];
   a12 =   c*r[1][2] + s*r[2][2];
   a20 = - s*r[1][0] + c*r[2][0];
   a21 = - s*r[1][1] + c*r[2][1];
   a22 = - s*r[1][2] + c*r[2][2];

   r[1][0] = a10;
   r[1][1] = a11;
   r[1][2] = a12;
   r[2][0] = a20;
   r[2][1] = a21;
   r[2][2] = a22;

   return;

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  All rights reserved.
**  
**  This library is derived, with permission, from the International
**  Astronomical Union's "Standards of Fundamental Astronomy" library,
**  available from http://www.iausofa.org.
**  
**  The ERFA version is intended to retain identical functionality to
**  the SOFA library, but made distinct through different function and
**  file names, as set out in the SOFA license conditions.  The SOFA
**  original has a role as a reference standard for the IAU and IERS,
**  and consequently redistribution is permitted only in its unaltered
**  state.  The ERFA version is not subject to this restriction and
**  therefore can be included in distributions which do not support the
**  concept of "read only" software.
**  
**  Although the intent is to replicate the SOFA API (other than
**  replacement of prefix names) and results (with the exception of
**  bugs;  any that are discovered will be fixed), SOFA is not
**  responsible for any errors found in this version of the library.
**  
**  If you wish to acknowledge the SOFA heritage, please acknowledge
**  that you are using a library derived from SOFA, rather than SOFA
**  itself.
**  
**  
**  TERMS AND CONDITIONS
**  
**  Redistribution and use in source and binary forms, with or without
**  modification, are permitted provided that the following conditions
**  are met:
**  
**  1 Redistributions of source code must retain the above copyright
**    notice, this list of conditions and the following disclaimer.
**  
**  2 Redistributions in binary form must reproduce the above copyright
**    notice, this list of conditions and the following disclaimer in
**    the documentation and/or other materials provided with the
**    distribution.
**  
**  3 Neither the name of the Standards Of Fundamental Astronomy Board,
**    the International Astronomical Union nor the names of its
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**    from this software without specific prior written permission.
**  
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**  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/