i have an error

Error, (in plots:-pointplot) number of elements in Vector must be a multiple of 2

that keeps popping up. What does it mean and how do I fix it?

I have been working on this for a while and Maple Support has been no help.

I have a series of unsimplified questions that I am solving for. I am trying to run it from 0 to 2*Pi and plot that against the value that is calculated for r3. it solves for opposites (positive and negative) and I only want the first set. From there I am unable to have the r3 value assigned as a value and then used for the calculation of r3a (which is just the array name).

here is my code and the errors that occur