8 / VERSION 5A 4-27-77 PT
43 FLDA% BPACOS,1 /ADDR OF X
48 JEQ ACOSEQ /IF 0 RTN PI OVER 2
54 JLE ACOSOK /IS IT <1.?
67 FDIV ACOS8 /SQRT (1-X^2)/X
71 JA .+4 /ATAN (SQRT(1-X^2)/X)
73 JXN ACSRTN,0 /NO SIGN CHG NECESSARY
74 FADD FPIACS /ADD PI IF MINUE
76 ACOSEQ, FLDA FPI2AC /RTN PI OVER 2 IF 0