# [Numpy-discussion] Error in tanh for large complex argument

Mark Bakker markbak at gmail.com
Fri Jan 28 05:45:09 EST 2011

Good point, so we need a better solution that fixes all cases

>> I'll file a ticket.
>>
>> Incidentally, if tanh(z) is simply programmed as
>>
>> (1.0 - exp(-2.0*z)) / (1.0 + exp(-2.0*z))

>This will overflow as z -> -\infty. The solution is probably to use a
>different expression for Re(z) < 0, and to check how other libraries do
>this in case the above still misses something.
>
>	Pauli
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