SpiceDouble twopi_c ( void )
Return twice the value of pi (the ratio of the circumference of
a circle to its diameter).
The function returns twice the value of pi.
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.
The first time the function is referenced, the value is computed
as shown above. The value is saved, and returned directly upon
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 / vnorm_c( n ) );
if ( node < 0.D0 )
node = node + twopi_c();
W.L. Taber (JPL)
I.M. Underwood (JPL)
E.D. Wright (JPL)
-CSPICE Version 1.0.0, 08-FEB-1998 (EDW)
twice the value of pi