twopi_c

Index Page twopi_c
A B C D E F G H I J K L M N O P Q R S T U V W X
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       SpiceDouble twopi_c ( void )
#### Abstract
       Return twice the value of pi (the ratio of the circumference of
       a circle to its diameter).
#### Required_Reading
       None.
#### Keywords
       CONSTANTS
#### Brief_I/O
       The function returns twice the value of pi.
#### Detailed_Input
       None.
#### Detailed_Output
       The function returns twice the value of pi (the ratio of
       a circle's circumference to its diameter), determined by
       the ACOS function. That is,

               twopi = acos ( -1. ) * 2.
#### Parameters
       None.
#### Exceptions
       Error free.
#### Files
       None.
#### Particulars
       The first time the function is referenced, the value is computed
       as shown above. The value is saved, and returned directly upon
       subsequent reference.
#### Examples
       The code fragment below illustrates the use of twopi_c.

            /.
                   The longitude of the ascending node is the angle
                   between the x-axis and the node vector, n.
                                                           -
            ./
                   node = acos ( n[0] / vnorm_c( n ) );

                   if ( node < 0.D0 )
                      {
                      node = node + twopi_c();
                      }
#### Restrictions
       None.
#### Literature_References
       None.
#### Author_and_Institution
       W.L. Taber      (JPL)
       I.M. Underwood  (JPL)
       E.D. Wright     (JPL)
#### Version
       -CSPICE Version 1.0.0, 08-FEB-1998 (EDW)
#### Index_Entries
       twice the value of pi
#### Link to routine twopi_c source file twopi_c.c

    Thu Apr 16 08:59:25 2009