result of acosh is never more precise than double 20 largest ulp errors (stored in a double) 1.49998 ulp for acosh(1.12762596520521274) = 0.499999999997758571) 1.49995 ulp for acosh(1.00754871630097775) = 0.122794447644565763) 1.49127 ulp for acosh(1.00754871629998832) = 0.122794447636528359) 1.43389 ulp for acosh(1.00754871629999676) = 0.122794447636596901) 1.00394 ulp for acosh(1.00782267781110768) = 0.124999999883478263) 1.00034 ulp for acosh(1.00782267782562651) = 0.124999999999326983) 0.91277 ulp for acosh(1.03141309987957275) = 0.249999999999998279) 0.60209 ulp for acosh(1.24959003930000034) = 0.692600317104164365) 0.60042 ulp for acosh(3.15772050439999985) = 1.81692618977516629) 0.59773 ulp for acosh(1.54308063481524393) = 1) 0.58186 ulp for acosh(1.03141309987957297) = 0.249999999999999167) 0.56814 ulp for acosh(1.26108743089999931) = 0.707752145215589934) 0.56656 ulp for acosh(3.48224220920001182) = 1.91953826890366108) 0.56356 ulp for acosh(1.99975071920000014) = 1.3168139626273172) 0.55608 ulp for acosh(81.8720922097000567) = 5.09826806028882284) 0.55552 ulp for acosh(78.9892779258999553) = 5.06241923039169706) 0.55344 ulp for acosh(2.62014632439999895) = 1.61779429270285369) 0.55323 ulp for acosh(1.00000000000000022) = 2.10734242554470173e-08) 0.55226 ulp for acosh(4.61376402280000075) = 2.2102343711924699) 0.55147 ulp for acosh(3.36504125080000005) = 1.88374017981709696) acosh10331.499981.127625965205212740.499999999997758571