Re: Wanted: a trick

• To: mathgroup at smc.vnet.net
• Subject: [mg3933] Re: Wanted: a trick
• From: rhall2 at umbc.edu (hall robert)
• Date: Fri, 10 May 1996 03:30:16 -0400
• Organization: University of Maryland, Baltimore County
• Sender: owner-wri-mathgroup at wolfram.com

```In article <4m7q5d\$k5h at dragonfly.wolfram.com>,
Robert Knapp  <rknapp at wolfram.com> wrote:
>Jinchul Park wrote:

>> a = b =  Exp[1 + 1.234 k] (k is a variable).
>>
>> I want to find t by dividing a by b such as
>>
>>                          0. k
>> t = a/b.  What I get is E.    How come the result is NOT '1' ?  In other
>>
>> words, why '0. k' is not calculated as '0'?
>>
>Mathematica keeps track of the difference between exact zeros (0) and
>inexact zeros (0.).  Since inexact zeros may be the result of roundoff
>or other approximate number errors, they are not made to be equal to and
>exact zero by default.
>
>> Is there any way to make 0. k as 0?
>>
>Yes,  The simplest way to convert inexact zeros to exact zeros is with
>the command Chop[]:
>
>In[1]:= a = b =  Exp[1 + 1.234 k]
>
>         1 + 1.234 k
>Out[1]= E
>
>In[2]:= a/b
>
>         0. k
>Out[2]= E
>
>In[3]:= Chop[%]
>
>Out[3]= 1
>
>
>> Also, in a simple symbolic calculation, 1.5 k - 1.5 k = '0. k' not '0.'  On
>>
>> the other hand, k - k = '0.'  Would you tell me what I need to do to get
>>
>> just '0' instead of '0. k'?
>>
>
>In[4]:= 1.5 k - 1.5 k
>
>Out[4]= 0. k
>
>In[5]:= Chop[%]
>
>Out[5]= 0

Factor[] and Together[] also work. But Chop[] may cut more Gordian knots.

--
Bob Hall            | "Know thyself? Absurd direction!
rhall2 at gl.umbc.edu  |  Bubbles bear no introspection."  -Khushhal Khan Khatak

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