<RectangleGeometry>

[FrmRectangleGeometry.xaml]

<UserControl x:Class="RiaGeometry.FrmRectangleGeometry"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    mc:Ignorable="d"

    d:DesignHeight="300" d:DesignWidth="400">

   

    <Grid x:Name="LayoutRoot" Background="White">

        <Ellipse Width="300" Height="100" Fill="Yellow" Stroke="Red">

            <Ellipse.Clip>

                <RectangleGeometry Rect="40,0 250,100">

                </RectangleGeometry>

            </Ellipse.Clip>       

        </Ellipse>

    </Grid>

</UserControl>