/*
 *  call-seq:
 *     dvector.sin   ->  a_dvector
 *  
 *  Returns of copy of _dvector_ with entry x replaced by sin(x).
 *     
 *     a = Dvector[ 1, -2, -3, 4 ]
 *     a.sin   -> Dvector[ sin(1), sin(-2), sin(-3), sin(4) ]
 */ 
VALUE dvector_sin(VALUE ary) {