Hi LEastburn,
Create a WPF application, open up the main form, put this inside your XAML. You may want to have the design view and the XAML view side by side.
<Canvas x:Name="LayoutRoot" Background="AliceBlue">
<Ellipse Height="150" Width="150" Canvas.Top="275" Canvas.Left="250" Stroke="LightSlateGray" StrokeThickness="2" />
<Ellipse Height="150" Width="150" Canvas.Top="275" Canvas.Left="100" Stroke="LightSlateGray" StrokeThickness="2">
<Ellipse.RenderTransform>
<RotateTransform CenterX="225" CenterY="75" Angle="120" />
</Ellipse.RenderTransform>
</Ellipse>
</Canvas>
Try changing the 'Angle' property of the 'RotateTransform' object of the second circle. You'll see it moves along the circumference. So what SA is 'trying' to tell you is, do this calculation in your application. There are couple of things you should remember.
1. Find the center of the other circle relative to the circle you want to rotate and set it to 'CenterX' and 'CenterY' properties of the RotateTranform
2. 'CenterX' and 'CenterY' must be specified relative to the circle in which they belong to. I.e. it's the distance from top-left corner of the circle, not the Canvas.
3. Since you want to move the circle along the circumference, do the necessary math and place it adjacent to the other circle.
After that all you have to do is, change the 'Angle' in RotateTransform or animate it, it will move around the circle.
Hope this helps, Cheers