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MathGroup Archive 2000

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Re: Re: 1/Trig function - help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24280] Re: [mg24261] Re: [mg24248] 1/Trig function - help
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Fri, 7 Jul 2000 00:11:23 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Hartmut

I noticed this too, after posting my first message. I considered sending a
second one just to point this out but than I noticed that using HoldForm in
this way may be a problem if one wanted to hold something else and then
apply ReleaseHold globally. All your Held expressions would then evaluate.
But of course this is a pretty unlikely situation, so this may well be the
best general solution.

Best regards

Andrzej

on 00.7.6 5:36 PM, Wolf Hartmut at hwolf at debis.com wrote:

> Dear Andrzej,
> 
> changing the output format is definitely the best way, I think. But then you
> need not rename Sin to sin nor Cos to cos. It suffices to take the HoldForm
> of the original functions. This then gives undisturbed calculus and a
> seemless, clear appearance in print:
> 
> 
> In[1]:= Unprotect[Csc, Sec];
> In[2]:= Format[Csc[x_]] := HoldForm[1/Sin[x]]
> In[3]:= Format[Sec[x_]] := HoldForm[1/Cos[x]]
> In[4]:= Protect[Csc, Sec];
> 
> In[5]:= D[Tan[x], x]
> Out[5]=
> 1    2
> (------)
> Cos[x]
> 
> In[6]:= % /. x -> 0
> Out[6]= 1
> 
> In[9]:= 1/Sin[y] 
> Out[9]=
> 1
> ------
> Sin[y]
> 
> In[10]:= % Cos[y]
> Out[10]= Cot[y]
> 
> 
>> -----Original Message-----
>> From: Andrzej Kozlowski [SMTP:andrzej at tuins.ac.jp]
To: mathgroup at smc.vnet.net
>> Sent: Thursday, July 06, 2000 5:11 AM
>> To: mathgroup at smc.vnet.net
>> Subject: [mg24280] [mg24261] Re: [mg24248] 1/Trig function - help
>> 
>> Here is one simple way which may perhaps be satisfactory:
>> 
>> In[11]:=
>> Unprotect[Csc, Sec];
>> In[12]:=
>> Format[Csc[x_]] := 1/sin[x];
>> In[13]:=
>> Format[Sec[x_]] := 1/cos[x];
>> In[14]:=
>> Protect[Csc, Sec];
>> 
>> 
>> Now,  for example:
>> In[15]:=
>> D[Tan[x], x]
>> Out[15]=
>> 1    2
>> (------)
>> cos[x]
>> 
>> You can still to comutations in the usual way:
>> 
>> In[16]:=
>> % /. x -> 0
>> Out[16]=
>> 1
>> 
>> Andrzej
>> -- 
>> Andrzej Kozlowski
>> Toyama International University, JAPAN
>> 
>> For Mathematica related links and resources try:
>> <http://www.sstreams.com/Mathematica/>
>> 
>> on 7/5/00 4:22 AM, zhl67 at my-deja.com at zhl67 at my-deja.com wrote:
>> 
>>> Hello,
>>> 
>>> For some reason I wish the trigonometric functions to the power of -1
>>> not automatically evaluated to some other trig functions. For instance,
>>> I wish the out put of
>>> 
>>> In[1]:= Sin[x]^(-1)
>>> 
>>> remain unchanged or appears as
>>> 
>>> 1
>>> Out[1]:=-------
>>> Sin[x]
>>> 
>>> but NOT Csc[x]. Is there any cost efficient way to do this? Adding
>>> rules to Power function might do(I only wish this feature for certain
>>> argumentx x), but it slows down the Power function at the same time.
>>> 
>>> Liu Zhao
>>> 
>>> 
>>> Sent via Deja.com http://www.deja.com/
>>> Before you buy.
>>> 
>> 
> 

-- 
Andrzej Kozlowski
Toyama International University
JAPAN

http://platon.c.u-tokyo.ac.jp/andrzej/
http://sigma.tuins.ac.jp/



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