hyperbolic cosine inverse
t = acosh(x)
each is a real or complex vector or matrix.
t
has the sizes of x
.
acosh(x)
returns t
such that
cosh(t)==x
and real(t)>=0
.
-t
are always other possible answers.
For real input numbers -1 < x < 1
,
real(t)==0
and imag(t)
belongs to ]0, %pi[
.
For complex numbers x
,
imag(t)
belongs to [-pi, pi]
and any t + k*%pi*%i
with integer k are other
possible answers.