00001 *DECK ACOSH 00002 FUNCTION ACOSH (X) 00003 C***BEGIN PROLOGUE ACOSH 00004 C***PURPOSE Compute the arc hyperbolic cosine. 00005 C***LIBRARY SLATEC (FNLIB) 00006 C***CATEGORY C4C 00007 C***TYPE SINGLE PRECISION (ACOSH-S, DACOSH-D, CACOSH-C) 00008 C***KEYWORDS ACOSH, ARC HYPERBOLIC COSINE, ELEMENTARY FUNCTIONS, FNLIB, 00009 C INVERSE HYPERBOLIC COSINE 00010 C***AUTHOR Fullerton, W., (LANL) 00011 C***DESCRIPTION 00012 C 00013 C ACOSH(X) computes the arc hyperbolic cosine of X. 00014 C 00015 C***REFERENCES (NONE) 00016 C***ROUTINES CALLED R1MACH, XERMSG 00017 C***REVISION HISTORY (YYMMDD) 00018 C 770401 DATE WRITTEN 00019 C 890531 Changed all specific intrinsics to generic. (WRB) 00020 C 890531 REVISION DATE from Version 3.2 00021 C 891214 Prologue converted to Version 4.0 format. (BAB) 00022 C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ) 00023 C 900326 Removed duplicate information from DESCRIPTION section. 00024 C (WRB) 00025 C***END PROLOGUE ACOSH 00026 SAVE ALN2,XMAX 00027 DATA ALN2 / 0.6931471805 5994530942E0/ 00028 DATA XMAX /0./ 00029 C***FIRST EXECUTABLE STATEMENT ACOSH 00030 IF (XMAX.EQ.0.) XMAX = 1.0/SQRT(R1MACH(3)) 00031 C 00032 IF (X .LT. 1.0) CALL XERMSG ('SLATEC', 'ACOSH', 'X LESS THAN 1', 00033 + 1, 2) 00034 C 00035 IF (X.LT.XMAX) ACOSH = LOG (X + SQRT(X*X-1.0)) 00036 IF (X.GE.XMAX) ACOSH = ALN2 + LOG(X) 00037 C 00038 RETURN 00039 END
1.7.1
