era.rx.md

eraRx

ERFA.rx(phi, r)

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)  )

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.