result of acos is never more precise than double

20 largest ulp errors (stored in a double)
   0.99442 ulp for acos(0.96891242171064895) = 0.24999999999998318)
   0.96506 ulp for acos(0.96891242171064629) = 0.24999999999999395)
   0.65230 ulp for acos(0.89597410960000068) = 0.46017653856740476)
   0.61244 ulp for acos(0.94245444879999762) = 0.34089909243822658)
   0.60575 ulp for acos(0.74706767740000046) = 0.72715643027096433)
   0.60512 ulp for acos(0.82145767919999957) = 0.60683387041870662)
   0.59764 ulp for acos(0.02701322340000005) = 1.5437798169933314)
   0.58981 ulp for acos(0.59497157119999955) = 0.93356604890309658)
   0.58250 ulp for acos(-0.67236890519999959) = 2.3082007697487996)
   0.57879 ulp for acos(0.55806340360000017) = 0.97874617911882555)
   0.57432 ulp for acos(-0.87501053019999886) = 2.6362538948207899)
   0.56327 ulp for acos(0.25712440660000041) = 1.3107509465927383)
   0.56141 ulp for acos(-0.45659141780000007) = 2.0449564816470804)
   0.55923 ulp for acos(-0.14509526800000008) = 1.7164055855579976)
   0.55433 ulp for acos(0.24112110459999997) = 1.3272754528329087)
   0.55337 ulp for acos(0.38833264820000019) = 1.1719747763936643)
   0.55275 ulp for acos(0.69174379519999984) = 0.80689530753108296)
   0.55264 ulp for acos(0.47928298940000003) = 1.0709587535417464)
   0.55219 ulp for acos(0.70542210520000015) = 0.7877778258763295)
   0.55134 ulp for acos(0.44511110299999995) = 1.1094979982520945)

<tr><td align=left><a href=acos.res>acos</a></td><td align=right>1308</td><td align=right>0.99442</td><td>0.96891242171064895</td><td>0.24999999999998318</td></tr>