Question: write math using textplot() and caption of plots[display]

Hi

I would like to display mathematical expressions on a plot.

I am using the following command on the code edit region of Maple 15 worksheet, intending to show the maths on a plot.

t := plots:-textplot([x, y, typeset(a[0]=1)], align = above): #where x and y are the position

 plots[display]([p,t],labels=["X","Y"],font=["Times","Roman",20],labeldirections=[default,vertical],axis=[gridlines=10],caption=typeset(eta[12]=0 , eta[21]=0)): # p is produced from a plot()

The display shows for the text plot , and                          

                                        
Questions;

1) Why didn't the textplot give a[0]=1

2) why didn't the caption show the "," inbetween eta[12]=0 and eta[21]=0

3) How could I improve the code to display a[0]=1 from the textplot and the comma on the caption

any help is appreciated.

thanks