I cannot plot a circle because it considers 'y' as an invalid character when it try to enter 'x^2 + y^2 = 1
How then do I plot circles, I cannot find it in the help library
i only found out today the answer to my question. although no one has answered it i guess i will share it for the benefit of everyone.
You have to define the circle as a parametric equation by clicking on graph->new parametric function, then a circle is defined by x=cos(t) and y=sin(t)
or you can define the circle on a polar graph and by clicking on graph->new polar graph, and type any number for r this will give a circle of radius r.
I expect that the software is programmed to normally have y = some function of x, and you would input the function of x. It can't have extra y's in the function.
So what you have to do is solve the equation for y first. You'll find you get two possibilities, y = sqrt(1 - x^2) and y = -sqrt(1 - x^2). You'll need to plot both of these separately.