We will show the difference between a Cam when we do not, and then we do add the Velocity Equations to the Maths FB.
A Cam is a good example, because we need the velocity of the CamFollower relative to the Cam before MechDesigner can find the correct Cam track coordinates.
We must symbolically differentiate the X and Y coordinate equations, given in Step 18.1, to find the velocity equations.
Remember, MechDesigner does these calculations automatically with a GearPair. We are doing this with a Maths FB only as an example of how to use the Maths FB.
The two Sliders move with the parametric equations to generate the the Epitrochoid Curve But, can we add a Cam and get the coordinates CamCoordinates? 

Add a CamFollower to the Piggyback Slider


Add a 2DCam


Cycle or Move the Master Machine to a different Machine Angle You can see the Cam does not follow the CamFollower. The Cam is nonsense. 
You need to differentiate the Parametric Curves for the Epitrochoid Curve with respect to t. To make your life easier, here are the two parametric equations for the velocity components:
These are written in the Maths FB as:


These are the 6 equations in the Maths FB:


Review the 2DCam You can see the Cam is correct. 