Thanks to Tomleslie for an easy way of my "hard way" method. I wish to describe why I persued the "hard way", and in the process it poses more questions about Maple - and some unanswered questions I originally asked.
I wanted to draw a circle colored green so I entered:
This produces a circle as if it had been drawn with a green crayon and compass. ...but I wanted the interior to be filled! ...so I next entered:
C1:=circle ([0,0],r, filled=true, color=green):
This did not give the required result - but neither did it give an error message! Searching on the help menu, there is nothing mentioned for 'filled'. That is why I resorted to the hard method. To my mind, a disk is a three dimensional entity, like a CD. A circle is 2D. I looked 'disk' in the dictionary and found that in North America, the words disk and circle are much the same: eg "the moon''s disk hung in a cloudless sky".
So I was duped by the American language😁 Questions posed are why did Maple 7 not flag an error message for filled=true?
In the rectangle command, what if one just wants to draw the perimeter of a rectangle? Wen the color option is used the recangle is automatically filled with colour.
And in my original post I drew a square comprising of a sequence of concentric rectangle commands, specifying color=white. Despite this, it draws a sequel of black squares! I have since experimented with the programme and it is sensitive to values of R (the radius of the circle, making the square of side 2R.) Try values of R = 49, 55 & 60 for differing results. One returns an error message.
Again, thanks, and any answers to my questions would me most appreciated.