Talk:Argument (complex analysis)

message: One should probably add a remark concerning the difference between Arg(z) and arg(z) (one is a set and one is an element of the reals).
: Done in latest version.— Kan8eDie (talk) 02:11, 11 February 2009 (UTC)
thread_title: Accuracy (?? Anon)

message: Hi. Here is the code in Maxima :
 /* principial value of argument of complex number in turns  */
 carg_t(z):=
 block(
  [t],
  t:carg(z)/(2*%pi),  /* now in turns */
  if t<0 then t:t+1, /* map from [-1/2,1/2) to [0, 1) */
  return(t)
 )$ 
Can I put it on page ?--Adam majewski (talk) 14:11, 11 January 2009 (UTC)
replies: text: This article is about the mathematical function. The atan2 function is the one used normally when computing arg. I can't see the point in putting code to derive it there either since the definition is perfectly good enough for a person to do that, and anyway most systems provide an atan2 to do the job faster and better. Plus the definition of arg and atan2 is normally from -pi to pi and you have explicitly changed that to something different. Plus Maxima isn't exactly mainstream. Dmcq (talk) 15:14, 11 January 2009 (UTC)
replies: text: Hi. Thx for answer.
* carg is function giving argument of complex number. it probably uses atan2.
* I have changed bad description in code . Now it shows that it uses turns as a units of arg. It is common practice in dynamical systems, complex analysis
* Maxima is a free, open source CAS. It uses Lisp.  Do you know better programs with that properities ? 
--Adam majewski (talk) 16:40, 11 January 2009 (UTC)

text: carg obviously stands for complex argument and gives the correct result by the definition. At best one could say is that carg implements arg which isn't exactly saying much. Turns is not the result defined for the result of arg whatever about its uses. I really can't see what your point is or why you would want to stick this in. Dmcq (talk) 18:02, 11 January 2009 (UTC)

text: See Comparison of computer algebra systems for various different CAS including open ones. Dmcq (talk) 18:08, 11 January 2009 (UTC)
replies: text:  OK. Thx.--Adam majewski (talk) 15:45, 15 January 2009 (UTC)
thread_title:  programing language 

message: As far as I understand, for the purpose of this article small "arg" is the mulitvalued function and capital Arg the well-defined function. To be consistent we should change all the "arg" into "Arg" in the "Identities" section then, I believe. bamse (talk) 13:44, 15 February 2009 (UTC)
replies: text: Wikipedia isn't a textbook, it should reflect general practice rather than being consistent. arg is generally used for both except if you're being formal and have to distinguish between them. Dmcq (talk) 23:02, 15 February 2009 (UTC)
replies: text: Alright, after all it states at the beginning of that section that it is the principal value arg. One more thing concerning amplitude. How about putting a warning as in Amplitude: In older texts the phase is sometimes very confusingly called the amplitude.? In fact, I had never seen the phase being called amplitude before. Being a physicist it is very confusing to me. Maybe mathematicians call it this way!? bamse (talk) 09:32, 16 February 2009 (UTC)
replies: text: Seems reasonable, it is confusing. It definitely has been called that and not all that uncommonly in the past,I wonder why anyone ever called it that never mind calling it argument. Some of the words in mathematics are very strange. Dmcq (talk) 13:03, 16 February 2009 (UTC)

text: In fact when talking about Jacobi elliptic functions there is a corresponding angle which is still talked of as the amplitude. Dmcq (talk) 13:13, 16 February 2009 (UTC)
thread_title:  Arg/arg 

message: The definition is not correct, for instance: 
:\!z1=1+i, \arctan(1/1) = \arg z1 =  \pi/4
:z2=-z1, \arctan (-1/-1) =  \pi/4 \neq \arg z2
The definition has to distinguish several possibilities. Nijdam (talk) 21:55, 5 October 2011 (UTC)
replies: text: You're quite right, the article was changed by someone in the last month to stick in that arctan. atan2 would do the trick but some people have this idea that atan2 isn't mathematical and insist on using arctan with the understanding that they just choose the angle in the way that atan2 does. It is really silly. I hate to think how many computer programs for instance have gone wrong because of people using arctan instead of atan2 as so many textbooks do this silly thing. I'll go and remove that arctan. Dmcq (talk) 00:17, 6 October 2011 (UTC)
thread_title:  Definition 

message: description of figure 3 mentions figure 4, which is missing in the article. EnTerbury (talk) 14:37, 19 October 2020 (UTC)
thread_title:  missing figure 

message: Could someone please add an explanation as to why this function became known as "argument", considering that, in mathematics, the word "argument" already has/had a widely-used different meaning? Gwideman (talk) 23:08, 2 October 2022 (UTC)
thread_title:  Why the name "arg"?