#include "slalib.h" #include "slamac.h" void slaCs2c ( float a, float b, float v[3] ) /* ** - - - - - - - - ** s l a C s 2 c ** - - - - - - - - ** ** Spherical coordinates to direction cosines. ** ** (single precision) ** ** Given: ** a,b float spherical coordinates in radians ** (RA,Dec), (long,lat) etc ** ** Returned: ** v float[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: 31 October 1993 ** ** Copyright P.T.Wallace. All rights reserved. */ { float cosb; cosb = (float) cos ( b ); v[0] = (float) cos ( a ) * cosb; v[1] = (float) sin ( a ) * cosb; v[2] = (float) sin ( b ); }