y = 90/x (1 <= x <= 90) のグラフで格子点をプロットする

hyper.tex

\documentclass[dvipdfmx,a4paper,10pt]{jsbook}
\usepackage{tikz}
\usepackage{ifthen}
\usepackage{calc}
\pagestyle{empty}
\begin{document}

\begin{tikzpicture}[line join=round,line cap=round,>=latex,x=1mm,y=1mm]
  \tikzset{AXIS/.style={color=black,thin,->}}
  \tikzset{GRID/.style={color=gray!50!white,very thin}}
  \def\MINT{0}\def\MAXT{90}\def\MINX{0}\def\MAXX{90}\def\MINY{0}\def\MAXY{90}

  \draw[AXIS] (\MINX,0) -- (\MAXX,0);
  \draw[AXIS] (0,\MINY) -- (0,\MAXY);

  \foreach \t in {\MINT,...,\MAXT} {
    \draw[GRID] (\MINX,\t) -- (\MAXX,\t);
    \draw[GRID] (\t,\MINY) -- (\t,\MAXX);
  }

  \newcounter{xy}
  \foreach \x in {\MINX,...,\MAXX} {
    \foreach \y in {\MINY,...,\MAXY} {
      \setcounter{xy}{\x*\y}
      \ifthenelse{\value{xy}=\MAXT} {
        \fill[red] (\x,\y) circle (1.5pt);
        \ifthenelse{\x < \y} {
          \draw (\x,\y) node[above right] {\tiny$(\x,\y)$};
        }{
          \draw (\x,\y) node[below left] {\tiny$(\x,\y)$};
        };
      }{};
    }
  }

\end{tikzpicture}

\end{document}