A plot of a curve's RadiusofCurvature is a good example because RadiusofCurvature needs the parametric velocity and acceleration equations for the X and Y coordinates.
We must symbolically differentiate the velocity equations, given in Step 18.2, to find the acceleration equations.
Remember, MechDesigner does these calculations automatically with GearPair. We are doing this with a Maths FB only as an example of how to use the Maths FB.
To plot the RadiusofCurvature for a Cam, we must


We can see graph is nonsense. 
You would need to differentiate the Velocity Equations we derived from the equations for the Epitrochoid Curve. To make your life easier, here are the two parametric equations for the acceleration components:
These are the acceleration equations written in the Maths FB:
It is important to click the 'Update' button to check the equations are valid. 

These are the equations in the Maths FB


Radius of Curvature of the Epicycloid Curve. 
We can now see the the plot for the RadiusofCurvature is as we expect. How can we check that the result is correct?


We can check the results by adding sketchcircles in the BaseParts with a radius equal to the values given in the graph. In this case I have added two Circles at the External and Internal RadiiofCurvature. The radius of the circles agree with the Radius of Curvature graph.
