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slalib/dcs2c.f

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+      SUBROUTINE sla_DCS2C (A, B, V)
+*+
+*     - - - - - -
+*      D C S 2 C
+*     - - - - - -
+*
+*  Spherical coordinates to direction cosines (double precision)
+*
+*  Given:
+*     A,B       d      spherical coordinates in radians
+*                         (RA,Dec), (long,lat) etc.
+*
+*  Returned:
+*     V         d(3)   x,y,z unit vector
+*
+*  The spherical coordinates are longitude (+ve anticlockwise looking
+*  from the +ve latitude pole) and latitude.  The Cartesian coordinates
+*  are right handed, with the x axis at zero longitude and latitude, and
+*  the z axis at the +ve latitude pole.
+*
+*  Last revision:   26 December 2004
+*
+*  Copyright P.T.Wallace.  All rights reserved.
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION A,B,V(3)
+
+      DOUBLE PRECISION COSB
+
+
+      COSB = COS(B)
+
+      V(1) = COS(A)*COSB
+      V(2) = SIN(A)*COSB
+      V(3) = SIN(B)
+
+      END