Вы можете просто повернуть путь с помощью RenderTransform:
<Path Width="296" Height="296" Stretch="Uniform"
Fill="Red" Stroke="Lime" StrokeThickness="8"
Data="M100,50 L50,87.5 50,62.5 0,62.5 0,37.5 50,37.5 50,12.5Z"
RenderTransformOrigin="0.5,0.5">
<Path.RenderTransform>
<RotateTransform Angle="{Binding ElementName=slider, Path=Value}" />
</Path.RenderTransform>
</Path>