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How can I write this equation in a nice manner when posting on Mathematica.SE?

Cos[Subscript[\[Beta], 0][t]] Sin[Subscript[\[Alpha], 0][t]] ==
  Cos[Subscript[\[Beta], i][t]] Sin[Subscript[\[Alpha], i][t]]
10
  • 4
    If you can at all avoid it, don't use Subscripts in your calculation. Not only does it improve readability, it also protects you from sneaky unintended behavior.
    – MarcoB
    Feb 23, 2016 at 19:18
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    You can format inline code and code blocks by selecting the code and clicking the {} button above the edit window. The edit window help button ? is also useful for learning how to format your questions and answers. You may also find this this meta Q&A helpful
    – Michael E2
    Feb 23, 2016 at 19:21
  • @MichaelE2 {} button : sorry but I didn't see this button
    – Bendesarts
    Feb 23, 2016 at 19:50
  • No problem. But since you're asking about formatting anyway, I thought I share my boilerplate advice to help folks discover the tools for making nice-looking posts.
    – Michael E2
    Feb 23, 2016 at 20:56
  • @MichaelE2 and so where is this button {} ?
    – Bendesarts
    Feb 23, 2016 at 20:58
  • Sorry, I thought you meant you didn't see it but now you do. If find it "above the edit window" as I said before. It's between the quote button and the image button. (By edit window, I mean the textbox for entering and editing the text of posts; I see it if I click on the "edit" button below your question.)
    – Michael E2
    Feb 23, 2016 at 21:30
  • @MichaelE2 ok of course, I believed that you were speaking in Mathematica. But, even if I use {}, I need to suppress subscript and symbols. {} doesn't make the transformation for me
    – Bendesarts
    Feb 23, 2016 at 21:33
  • But it transformed the text in the question into properly formatted code, instead of being formatted as a quotation, which is how it was originally formatted. (It was a comment about formatting your question itself, not an answer to your question.)
    – Michael E2
    Feb 23, 2016 at 21:35
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    You should avoid using Subscript while defining symbols (variables). Subscript[x, 1] is not a symbol, but a compound expression where Subscript is an operator without built-in meaning. You expect to do $x_1=2$ but you are actually doing Set[Subscript[x, 1], 2] which is to assign a Downvalue to the oprator Subscript and not an Ownvalue to an indexed x as you may intend. Read how to properly define indexed variables here
    – rhermans
    Feb 24, 2016 at 9:08
  • I am definitely in the minority on subscripts but I agree it is best to avoid when posting to Mathematica.SE -- unless the problem at hand specifically relates to subscripts. For subscript usage in general I recommend using the Notations package. Surprisingly, for what it is, Mathematica handling of subscripts has never come close to e.g. Mathcad or Maple, but the Notations package can get you a fair way as long as you stick within its limitations. Apr 27, 2017 at 2:55

2 Answers 2

5

Try this:

expr = Cos[Subscript[\[Beta], 0][t]] Sin[Subscript[\[Alpha], 0][t]] ==
   Cos[Subscript[\[Beta], i][t]] Sin[Subscript[\[Alpha], i][t]]

Mathematica graphics

expr /. Subscript[a_, b_] -> a[b]

(* Out: Cos[\[Beta][0][t]] Sin[\[Alpha][0][t]] == Cos[\[Beta][i][t]] Sin[\[Alpha][i][t]]*)

You can then use http://steampiano.net/msc/ to get:

Cos[β[0][t]] Sin[α[0][t]] == Cos[β[i][t]] Sin[α[i][t]]
5
  • Nice, but there are always corner cases Subscript[b, Sequence @@ {a, u}] /. Subscript[a_, b_] -> a[b] Feb 24, 2016 at 20:42
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    @Dr.belisarius Agreed, this is a partial solution at best. I honestly don't think the effort it would take to make this approach more general would be worthwhile. It's much easier to fix the problem at the root by avoiding subscripts altogether :-)
    – MarcoB
    Feb 25, 2016 at 5:27
  • Absolutely, completely, unconditionally agree Feb 25, 2016 at 5:29
  • @MarcoB And how can I do when I have several levels of subscripts ? I have tried this when I have expressions with 2 or 3 levels but it doesn't work : Map[ToString, q3Pattes /. Or[Subscript[a_, b_] -> a[b], Subscript[a_, b_, c_] -> a[b[c]]]] Do you have ideas why ?
    – Bendesarts
    Feb 27, 2016 at 21:32
  • Perhaps Subscript[a_, b_, c_] -> a[b, c]? There won't be any perfect solution; the unfortunate truth is that a lot of hand-conversion may be needed.
    – MarcoB
    Feb 27, 2016 at 22:35
3

The short answer is that there is no easy way to do what you ask. The editor we use on Mathematica.SE website does not support entry and display of two-dimensional forms nor does it convert Mathematica's special character notation to Unicode.

Some amelioration is possible, depending on your intent for posting the code.

  • For special characters that have Unicode equivalents, install halirutan's plug-in into your web browser (see Additional useful buttons for our M.SE editor) and use the αβ button that it adds to our editor to make the conversion.

  • If the snippet you are pasting in represents Mathematica output, then you can insert a PNG image of the output into your post rather than pasting in text.

  • If the snippet you are pasting represents input to Mathematica, then you might post the expression both as text and as a PNG image of the input. Do not post a PNG image without a text version.

As others have already mentioned there are good, solid, technical reasons for avoiding the use of Subscript expressions in Input cells (cells that get evaluated). I, myself, never use them in Input cells. Pretty formatting does not compensate sufficiently for the problems Subscript expressions can cause in evaluations.

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