Set SweepDirection=Clockwise for ArcSegment
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="WPF" Height="200" Width="250">
<Canvas Margin="10">
<Path Canvas.Left="70" Stroke="Black" StrokeThickness="3">
<Path.Data>
<GeometryGroup>
<PathGeometry>
<PathFigure IsClosed="True" StartPoint="40,0">
<ArcSegment Point="170,110" IsLargeArc="True" Size="10,10" SweepDirection="Clockwise"/>
</PathFigure>
</PathGeometry>
</GeometryGroup>
</Path.Data>
</Path>
</Canvas>
</Window>
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