Lines Matching defs:acosh
923 /* acosh(x)
926 * acosh(x) = log [ x + sqrt(x*x-1) ]
928 * acosh(x) := log(x)+ln2, if x is large; else
929 * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
930 * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
933 * acosh(x) is NaN with signal if x<1.
934 * acosh(NaN) is NaN without signal.
936 double acosh(double x) {
950 return log(x) + ln2; /* acosh(huge)=log(2x) */
953 return 0.0; /* acosh(1) = 0 */