           SpiceDouble             s;
            SpiceDouble             v1[3];
            SpiceDouble             v2[3];
            SpiceDouble             v3[3];

            s = sqrt(3.0)/2;

            <a href="vpack_c.html">vpack_c</a> (   s,  -0.5,  0.0, v1 );
            <a href="vpack_c.html">vpack_c</a> ( 0.0,   1.0,  0.0, v2 );
            <a href="vpack_c.html">vpack_c</a> (  -s,  -0.5,  0.0, v3 );

            <b>pltnrm_c</b> ( v1, v2, v3, normal );

            printf ( &quot;NORMAL = %18.1