Unable to plot

[FC_10037391]

Even providing all the inputs the lot will still not plot 

[LucMeekes]

You define Ay(t) and Cy(t), and want to plot Py(t),,,?

Success!
Luc

[FC_10037391]

My bad it is Cy(t) against t. I also tried to add the units but still getting the error 

[LucMeekes]

OK. You're using symbolic evaluation in your definitions of Ay and Cy. Prime is capable of such things, but (too) often creates a mess.

See how some of your units remain units (bold blue italic) and some don't.

The better way to work with symbolics is to stay symbolic until you need to input values. Something like this:

Success!

Luc

[Werner_E · Accepted solution]

Primes auto-labelling, especially in connection with units and symbolic evaluation most of the time is a PITA.

But in case of your problem, the simple solution is to turn on "Units/Constants in Symbolics" in the calculation options.

You can leave your worksheet unchanged otherwise - despite changing P.y to C.y of course: