result of acos is never more precise than double 20 largest ulp errors (stored in a double) 14.00004 ulp for acos(0.992197667229687053) = 0.124999999997128339) 7.49965 ulp for acos(0.992197667223120305) = 0.125000000049799359) 6.49999 ulp for acos(0.992197667228592595) = 0.125000000005907219) 6.49758 ulp for acos(0.99219766722932401) = 0.125000000000040273) 5.50008 ulp for acos(0.992197667229261504) = 0.125000000000541955) 4.98056 ulp for acos(0.992197667229329339) = 0.124999999999997641) 4.31450 ulp for acos(0.992197667229329117) = 0.124999999999999431) 3.49941 ulp for acos(0.992197667229322677) = 0.125000000000051043) 3.00558 ulp for acos(0.968912421710648952) = 0.249999999999983069) 3.00000 ulp for acos(0.968912421710740213) = 0.249999999999614364) 1.74074 ulp for acos(0.992197667229329006) = 0.125000000000000333) 1.51236 ulp for acos(0.947947697000000256) = 0.324068670750073895) 1.50169 ulp for acos(0.9520198747999844) = 0.311026665707379746) 1.50049 ulp for acos(0.904317894799978039) = 0.441017281524431759) 1.50038 ulp for acos(0.952019874800020705) = 0.311026665707261285) 1.50004 ulp for acos(0.952019874799638788) = 0.311026665708509231) 1.50000 ulp for acos(0.926453970398442239) = 0.385916162950105668) 1.50000 ulp for acos(0.962390530996234506) = 0.275127634630110918) 1.50000 ulp for acos(0.900249455000380117) = 0.450454184228385346) 1.49999 ulp for acos(0.947947696993703959) = 0.324068670769847078) acos130814.000040.9921976672296870530.124999999997128339