Re: 1.5! on TI-83?

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Re: 1.5! on TI-83?
From: RWW Taylor <RWTNTS@RITVAX.ISC.RIT.EDU>
Date: Sun, 31 May 1998 12:12:02 -0400
Reply-To: RWW Taylor <RWTNTS@RITVAX.ISC.RIT.EDU>

> Thanks for the response.
>
> But why does the TI-83 compute 1.5! (via the gamma function)
> and not 1.6! ?

The reference in the TI archives explains this.  Because gamma(-0.5) has a
"nice" value (easily understood, involving as it does the square root of pi)
and gamma obeys a simple recursive rule, evaluation of gamma for values n+0.5
where n is a non-negative integer can be done quite simply, and the power
to do this (a well as the power to calculate the value of n factorial for
small values of n) was built into the TI-83.

As to _why_ this was considered a desirable thing to do, please check the
web site...

RWW Taylor
National Technical Institute for the Deaf
Rochester Institute of Technology
Rochester NY 14623

>>>> The plural of mongoose begins with p. <<<<

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