Cfrgtkky

I don't know why, but the math equation looks very small in my tcolorbox poster. Any idea why?

Thanks!

MWE:

documentclass[12pt]{article}

usepackage[utf8]{inputenc}

usepackage[T1]{fontenc} % To switch to the T1 encoding

% usepackage{lmodern} % To switch to Latin Modern

usepackage{palatino}

usepackage{amssymb, amsthm, amsmath}



usepackage[a0paper]{geometry}

usepackage[poster,most]{tcolorbox}



pagestyle{empty}



begin{document}

begin{tcbposter}[

    coverage = {

      spread,

      % interior style={top color=yellow,bottom color=yellow!50!red},

      top=25mm, bottom=25mm, left=15mm, right=15mm,

    },

    poster   = {showframe=false,columns=3,rows=5,spacing=13mm},

    boxes    = {

      enhanced standard jigsaw,sharp corners=downhill,

      arc=10mm, boxrule=2mm,

      coltitle=black!85,

      boxsep=0pt,

      top=15mm,bottom=15mm,right=15mm,left=15mm,

      colback=white,opacityback=0.75,colframe=cyan!30!white!90!black,

      title style={left color=cyan!20!white!90!black,

        right color=cyan!20!white!90!black,

      },

      fonttitle=Largescshapebfseries,

      valign=center,

    },

    fontsize = 36pt

    ]



  posterbox[blankest,interior engine=path,height=10cm,

    halign=center,valign=center,colupper=black,

    ]{name=title,column=1,span=3,below=top}{

    {Hugebftextsc{I Want A Title With\[.3em]

        Small Caps Enabled}}\[.3em]

    textsc{Here are Some Names}

  }



  posterbox[adjusted title=Security]

  {name=security,below=title,column=2,span=1}{

    I am some text, and here is a formula $hc(x,r) = sum x_i r_i bmod 2$, isn't it strange to have such a small formula?

    $$hc(x,r) = sum x_i r_i bmod 2$$

  }



end{tcbposter}

end{document}

-- EDIT --
Using usepackage[bitstream-charter]{mathdesign} as proposed in comments works indeed (thanks!), but this font is a bit too different from the default one. The lmodern font on the other side gives an ugly sum symbol:

The problem is that the default math font you are using is not available in the size you request it. As a workaround use a math font with is scalable to this size.

If you want to keep the look of the default math font, you could comment in the lmodern package you already have in your preamble and fix some remaining problems with the exscale package:

usepackage{lmodern} 

usepackage{palatino}

usepackage{exscale}

Personally I would combine your palatino font with a math font which is a bit heavier

usepackage{amssymb, amsthm, amsmath}

usepackage[bitstream-charter]{mathdesign}

usepackage{palatino}

Or use a similar font which also provides math. This will also save you from using the outdated palatino package.

usepackage{newpxtext,newpxmath}