Result of:    j=0 indicates x too small
             j=100 indicates x too large
      locate:   guess   j      xx(j)     xx(j+1)
   -90.000000     5     0   lower lim  -72.948730
   -80.000000    10     0   lower lim  -72.948730
   -70.000000    15    27  -70.142578  -69.944801
   -60.000000    20    52  -60.536263  -59.845959
   -50.000000    25    63  -50.663933  -49.467468
   -40.000000    30    70  -40.884548  -39.186684
   -30.000000    35    75  -31.478916  -29.298817
   -20.000000    40    79  -22.064632  -19.401852
   -10.000000    45    83  -10.565994   -7.313683
     0.000000    50    86   -0.300194    3.478455
    10.000000    55    88    7.450874   11.626930
    20.000000    60    90   16.017128   20.632423
    30.000000    65    92   25.484306   30.584999
    40.000000    70    94   35.947151   41.584282
    50.000000    75    96   47.510437   53.740379
    60.000000    80    97   53.740379   60.289795
    70.000000    85    99   67.174942   74.413162
    80.000000    90   100   74.413162   upper lim
    90.000000    95   100   74.413162   upper lim