Re: TI-85 and log(-4)

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Re: TI-85 and log(-4)
From: Kenneth Fink <kfink@POSTOFFICE.WORLDNET.ATT.NET>
Date: Thu, 24 Jul 1997 19:09:38 GMT
Organization: AT&T WorldNet Services
References: <33d7a2ec.6217070@news.aristotle.net>
Reply-To: Kenneth Fink <kfink@POSTOFFICE.WORLDNET.ATT.NET>
Xref: paladin.american.edu bit.listserv.calc-ti:15428

On Thu, 24 Jul 1997 18:56:52 GMT, dsocher@aristotle.net (David Socher)
wrote:

by using infinite series, it can be shown that

e^(ix)=cos(x) + i*sin(x)

therefore, if x was pi, then e^(pi*i) = -1
you can take the ln of that, so ln (-1) = pi*i

thus, you can take logs of negative numbers because of this
relationship



>My algebra instructor had everyone punch the log of a negative number
>into their calculator to demonstrate that this could not be done.
>Everyone got an error message except me and my TI-85.  I got something
>that looks like a complex number.  My instructor couldn't explain it.
>The manual doesn't to cover it.  Can anyone tell me what's happening
>here?
>
>David Socher

References:

TI-85 and log(-4)

From: David Socher <dsocher@ARISTOTLE.NET>

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