\Tau causes an error

Question

I use https://oeis.org/wiki/List_of_LaTeX_mathematical_symbols for symbols. It normally works. but when i want to use \Tau (or any greek symbols whose code starts with a capital for that matter) I get the error "Undefined control sequence. l.142 ... \in \mathbb{N}} $ dizisini $ x_n = \Tau " how do I fix this?

Your link references a non-TeX system that makes \Tau available. Since a greek Tau would look like a latin T there's no command for it. Just use a T. — Qrrbrbirlbel, Dec 08 '22 at 12:53
"or any greek symbols whose code starts with a capital" doubt that, try \Gamma, or \Pi. As @Qrrbrbirlbel states the reason \Tau doesn't work is because it looks just like T and so to save space (which was a concern back in the days more than now) the Greek letters which just look like Latin ones weren't defined. — Skillmon, Dec 08 '22 at 13:00
Somewhat related question, symbols - omicron not working in LaTeX - TeX - LaTeX Stack Exchange // fonts - How to write capital alpha? - TeX - LaTeX Stack Exchange — user202729, Dec 08 '22 at 14:20

score 4 · Answer 1 · answered Dec 08 '22 at 13:45

The command \Tau is defined when unicode-math is used, because it must refer to the Greek letter.

In legacy TeX there is no such command, because a Tau has the same shape as a T. The same for

\Alpha \Beta \Epsilon \Zeta \Eta \Iota \Kappa \Mu \Nu \Omicron \Rho \Chi

because the corresponding glyphs have the same shape as a Latin Letter.

You might want to say

\providecommand{\Tau}{\mathrm{T}}
\providecommand{\varTau}{T}

to get, respectively, the upright Tau (actually a T) and the slanted one, like for \varGamma and \varPi.

Add also the commands for the other letters, if you want.

\Tau causes an error

1 Answers1