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 ==== [MESSAGE SEPARATOR] ====