我怎样才能遮蔽该区域

Question

\documentclass {article}
\usepackage[utf8]{inputenc}
\usepackage[spanish]{babel}
\usepackage{parskip}
\usepackage{amsmath}
\usepackage{geometry}
\geometry{top=2cm, bottom=2cm, left=4.5cm, right=4.5cm}
\usepackage{setspace}
\usepackage{lipsum}
\usepackage{enumitem}
\usepackage{tikz,pgfplots}
\pgfplotsset{compat=1.18}
\usetikzlibrary{arrows.meta}
\usepgfplotslibrary{fillbetween}

\title{E11}
\author{Ing. Luque }
\date{\today}

\begin{document}
\maketitle
\section{Enunciado}

\begin{figure}[h!]
\LARGE
    \centering
    \begin{tikzpicture}
    \begin{axis}[x=1cm, xtick distance = 10, y=1cm, ytick distance = 10,xmin=-1,xmax=6,ymin=-1,ymax=6,axis x line =center, axis y line =center,xlabel=$X$,ylabel=$Y$, x label style={at={(ticklabel* cs:1.15)}},y label style={at={(ticklabel* cs:1.1)}},
    axis line style={-{Stealth[scale=1.2]}}]
    \draw[very thick] (3,0)--(3,3);
    \draw[very thick] (0,3)--(3,3);

    \draw[very thick, name path=B] (0, 4.2426) arc (90 : 0 : 4.2426);
    \node[below] at (3,0){A};
    \node[left] at (0,3){C};
    \node[right] at (3,3.2){B};
    \node[below] at (-0.3,0){O};
    \end{axis}

    \end{tikzpicture}


\end{figure}
\end{document}
[![enter image description here][1]][1]

Answer 1

像这样：

代码：

\documentclass[10pt,a4paper]{article}
\usepackage{tikz}

\begin{document}
    \begin{tikzpicture}[]
        \begin{scope}
            \clip (0,0) rectangle (4,3);
            \fill[blue] (0,0) circle(2.1213);
            \fill[white] (0,0) rectangle (1.5,1.5);
        \end{scope}
            \draw[-latex] (-.5,0)--(3,0) node[right] {$X$};
        \draw[-latex] (0,-.5)--(0,3) node[above] {$Y$};
        \draw (-.2,-.2) node {O};
        \draw (1.5,-.2) node {A};
        \draw (1.7,1.7) node {B};
        \draw (-.2,1.5) node {C};
    \end{tikzpicture}
    
\end{document}

添加：如果您需要所有图片：

代码是：

\documentclass[10pt,a4paper]{article}
\usepackage{tikz}

\begin{document}
    \begin{tikzpicture}[]
        \begin{scope}
            \clip (0,0) rectangle (4,3);
            \draw (0,0) circle(2.1213);
            \draw (0,0) rectangle (1.5,1.5);
        \end{scope}
        \draw[-latex] (-.5,0)--(3,0) node[right] {$X$};
        \draw[-latex] (0,-.5)--(0,3) node[above] {$Y$};
        \draw (-.2,-.2) node {O};
        \draw (1.5,-.2) node {A};
        \draw (1.7,1.7) node {B};
        \draw (-.2,1.5) node {C};
        \draw[line width=3pt,-latex] (4,1.5)--(5,1.5);
        \begin{scope}[xshift=6cm,yshift=0]
            \begin{scope}
                \clip (0,0) rectangle (4,3);
                \fill[blue] (0,0) circle(2.1213);
                \fill[white] (0,0) rectangle (1.5,1.5);
            \end{scope}
            \draw[-latex] (-.5,0)--(3,0) node[right] {$X$};
            \draw[-latex] (0,-.5)--(0,3) node[above] {$Y$};
            \draw (-.2,-.2) node {O};
            \draw (1.5,-.2) node {A};
            \draw (1.7,1.7) node {B};
            \draw (-.2,1.5) node {C};
        \end{scope}
    \end{tikzpicture}
    
\end{document}