The OpenD Programming Language

acosh

Calculates the inverse hyperbolic cosine of x.

Mathematically, acosh(x) = log(x + sqrt( x*x - 1))

$1 $2

Special Values
x	acosh(x)
NaN	NaN
<1	NaN
1	0
+∞	+∞

real acosh(real x)
double acosh(double x)
@safe pure nothrow @nogc
double
acosh
(
double x
)
float acosh(float x)

Examples

import std.math.traits : isIdentical, isNaN;

assert(isNaN(acosh(0.9)));
assert(isNaN(acosh(real.nan)));
assert(isIdentical(acosh(1.0), 0.0));
assert(acosh(real.infinity) == real.infinity);
assert(isNaN(acosh(0.5)));

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Source

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std math trigonometry functions