I want to write in math mode the real part of a complex number and I used the command \mathcal{R}(i). The problem is that the R it produces is not the same as the R in most books that represent the real part. One reason is that it is small and it shouldn't be as it is not meant as a letter but as a symbol. Using the \mathcal{F} I had the same problem representing the Fourier Transform. What command do you use and you think is best and most beuatiful for there operations?

  • 3
    There's no universal symbol for the three entities; some use fraktur ℜ and ℑ for the real and imaginary part of a complex number (\Re and \Im are predefined for this). I've seen several symbols for the Fourier transform: pick one an be consistent across a paper. Better yet, do \newcommand{\FT}{\mathcal{F}}$ and use \FT: you'll be able to change all appearances by just modifying this definition.
    – egreg
    Sep 12, 2014 at 15:15
  • What can I do about the size of the letter?
    – Adam
    Sep 12, 2014 at 15:19
  • I'm not sure I understand.
    – egreg
    Sep 12, 2014 at 15:27
  • 1
    In the books I have the impression that it is represented a lot bigger.
    – Adam
    Sep 12, 2014 at 15:50
  • 1
    Isn't the real part of an imaginary number 0? ;-) Sep 12, 2014 at 19:43

1 Answer 1


Please choose what you like. If you are not able to use Lua- or XeLaTeX, let me know.

% arara: lualatex

\newcommand*{\enlarge}[1]{\mathlarger{\mathlarger #1}}

        Font & Normal & Bold & Big\\\midrule
        Latin Modern Math & $\Re(i)\mscrR(i) \mscrF$&$\mbffrakR(i)\mbfscrR(i)\mbfscrF$&$\enlarge{\Re}(i)\enlarge{\mscrR}(i) \enlarge{\mscrF}$\\
        XITS Math & \setmathfont{XITS Math}$\Re(i)\mscrR(i) \mscrF$&$\mbffrakR(i)\mbfscrR(i)\mbfscrF$&$\enlarge{\Re}(i)\enlarge{\mscrR}(i) \enlarge{\mscrF}$\\
        Asana Math & \setmathfont{Asana Math}$\Re(i)\mscrR(i) \mscrF$&$\mbffrakR(i)\mbfscrR(i)\mbfscrF$&$\enlarge{\Re}(i)\enlarge{\mscrR}(i) \enlarge{\mscrF}$\\
        TeX G. P. Math & \setmathfont{TeX Gyre Pagella Math}$\Re(i)\mscrR(i) \mscrF$&$\mbffrakR(i)\mbfscrR(i)\mbfscrF$&$\enlarge{\Re}(i)\enlarge{\mscrR}(i) \enlarge{\mscrF}$\\\bottomrule

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