我想给椭圆的第一象限涂阴影，请指点

Question

请参阅下面的椭圆代码，我想为椭圆的第一象限添加阴影，请指导我该怎么做。提前致谢。

\begin{tikzpicture}

\draw (-5,0)--(5,0) (4.1,0)node{A} (0,3)--(0,-3)(0,2.2)node{B};
\draw(0,0)node{O}circle[x radius = 4 cm , y radius = 2 cm]; 

\end{tikzpicture}

Answer 1

\documentclass[tikz,border=3mm]{standalone}
\begin{document}
\begin{tikzpicture}
 \fill[red] (4,0) arc[x radius = 4 cm , y radius = 2 cm,start angle=0,end
 angle=90] |- cycle;
 \draw (-5,0)--(5,0) (4.1,0)node{A} (0,3)--(0,-3)(0,2.2)node{B};
 \draw(0,0)node{O}circle[x radius = 4 cm , y radius = 2 cm]; 
\end{tikzpicture}
\end{document}

如果您确实想将节点放在轴的顶部，请考虑使用contour。

\documentclass[tikz,border=3mm]{standalone}
\usepackage{contour}
\begin{document}
\begin{tikzpicture}
 \fill[red] (4,0) arc[x radius = 4 cm , y radius = 2 cm,start angle=0,end
 angle=90] |- cycle;
 \draw (-5,0)--(5,0) (4,0)node[right]{\contour{white}{$A$}} 
  (0,3)--(0,-3) (0,2)node[above]{\contour{white}{$B$}};
 \draw(0,0)node{\contour{white}{$O$}} 
 circle[x radius = 4 cm , y radius = 2 cm]; 
\end{tikzpicture}
\end{document}