[PD] tanh approximation

Andy Farnell padawan12 at obiwannabe.co.uk
Tue Oct 7 15:29:25 CEST 2008

Yep, they both converge on tanh afaics. 
Your one is more efficient though, I'll use that.

But what I don't understand is why it needs scaling and doesn't
naturally work over -1 to +1 



On Tue, 7 Oct 2008 14:46:56 +0200
Thomas Grill <gr at grrrr.org> wrote:

> Hi,
> > An approximation to tanh(x) is a continued fraction
> > x/1+ (x^2)/3+ (4x^2)/5+ (16x^2)/9+ ...
> are you sure this is correct?
> Another well-known formulation is x/(1+x^2/(3+x^2/(5+x^2/(7+.....
> which works for me and converges quickly.
> see http://nrich.maths.org/public/viewer.php?obj_id=1451
> gr~~~

Use the source
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