function asinh (x) c april 1977 edition. w. fullerton, c3, los alamos scientific lab. dimension asnhcs(20) external csevl, inits, r1mach data aln2 /0.6931471805 5994530942e0/ c c series for asnh on the interval 0. to 1.00000d+00 c with weighted error 2.19e-17 c log weighted error 16.66 c significant figures required 15.60 c decimal places required 17.31 c data asnhcs( 1) / -.1282003991 1738186e0 / data asnhcs( 2) / -.0588117611 89951768e0 / data asnhcs( 3) / .0047274654 32212481e0 / data asnhcs( 4) / -.0004938363 16265361e0 / data asnhcs( 5) / .0000585062 07058557e0 / data asnhcs( 6) / -.0000074669 98328931e0 / data asnhcs( 7) / .0000010011 69358355e0 / data asnhcs( 8) / -.0000001390 35438587e0 / data asnhcs( 9) / .0000000198 23169483e0 / data asnhcs(10) / -.0000000028 84746841e0 / data asnhcs(11) / .0000000004 26729654e0 / data asnhcs(12) / -.0000000000 63976084e0 / data asnhcs(13) / .0000000000 09699168e0 / data asnhcs(14) / -.0000000000 01484427e0 / data asnhcs(15) / .0000000000 00229037e0 / data asnhcs(16) / -.0000000000 00035588e0 / data asnhcs(17) / .0000000000 00005563e0 / data asnhcs(18) / -.0000000000 00000874e0 / data asnhcs(19) / .0000000000 00000138e0 / data asnhcs(20) / -.0000000000 00000021e0 / c data nterms, xmax, sqeps /0, 0., 0./ c if (nterms.ne.0) go to 10 nterms = inits (asnhcs, 20, 0.1*r1mach(3)) sqeps = sqrt (r1mach(3)) xmax = 1.0/sqeps c 10 y = abs(x) if (y.gt.1.0) go to 20 c asinh = x if (y.gt.sqeps) asinh = x*(1.0 + csevl (2.*x*x-1., asnhcs,nterms)) return c 20 if (y.lt.xmax) asinh = alog (y + sqrt(y**2+1.)) if (y.ge.xmax) asinh = aln2 + alog(y) asinh = sign (asinh, x) c return end