Question 1001939
{{{drawing(400,400,-5,5,-5,5, graph(400,400,-5,5,-5,5),line(-7,8,7,-6),
 red(arc(0,0,2,-2,0,90)), green(arc(0,0,2,-2,90,360)),


circle(3,2,0.09),circle(3,2,0.07),circle(3,2,0.05),circle(3,2,0.03),circle(3,2,0.01), locate(3,2,"(3,2)")





 )}}}
<pre>
All points of the form 

{{{(matrix(1,3, sin(theta)^"",",",cos(theta)))}}}

lie on the unit circle.  The ones on the same side of the line
x+y=1 as (3,2) are on the red part of the unit circle pictured
above, not on the green part.     

All the points on the red part have non-negative x and y coordinates
all between 0 and 1, inclusively.  So {{{theta}}} is a first quadrant
angle or {{{2pi*n<=theta<=pi/2+2pi*n}}}, for any integer n.

Edwin</pre>