result of acos is never more precise than double 20 largest ulp errors (stored in a double) 0.57432 ulp for acos(-0.875010530199998859) = 2.63625389482078987) 0.56589 ulp for acos(0.494714052400000104) = 1.05329055848079278) 0.56359 ulp for acos(-0.285180097800000198) = 1.85999065028581079) 0.56158 ulp for acos(-0.302041160800000263) = 1.87762942076527395) 0.55923 ulp for acos(-0.145095268000000083) = 1.7164055855579976) 0.55433 ulp for acos(-0.500537836800000191) = 2.09501625425507765) 0.55433 ulp for acos(0.241121104599999969) = 1.32727545283290871) 0.55318 ulp for acos(-0.278138884200000158) = 1.85265232029069038) 0.55264 ulp for acos(0.479282989400000026) = 1.07095875354174641) 0.55261 ulp for acos(-0.176508975199999946) = 1.74823493039029243) 0.55134 ulp for acos(0.445111102999999952) = 1.1094979982520945) 0.55042 ulp for acos(-0.741702368000000223) = 2.4064012216343853) 0.54904 ulp for acos(-0.479878203799998904) = 2.07131220875438515) 0.54853 ulp for acos(-0.416441785999999925) = 2.00032439479680413) 0.54583 ulp for acos(-0.148771287399999924) = 1.72012194304998056) 0.54422 ulp for acos(-0.491538323600000049) = 2.08465165104585637) 0.54364 ulp for acos(0.162448403800000113) = 1.40762481427990549) 0.54262 ulp for acos(-0.566778108599999553) = 2.17338622021293482) 0.53956 ulp for acos(-0.477825138199998833) = 2.06897358675603549) 0.53858 ulp for acos(0.29415766839999985) = 1.27222225190449212)