The general representation for circle is 
.
. The above 
is a parabola this is reason for getting lines instead of circle.
is a parabola this is reason for getting lines instead of circle.As an example
r=2; % radius of circle
x0=0; % x center of circle
y0=0; % y center of circle
syms x y
fimplicit((x-x0).^2 + (y-y0).^2 -r^2); %plot circle
Similary you can get circle co-ordinates using 
and 
and plot them if radius, center of circle is given
and and plot them if radius, center of circle is givenr=2;
x=0;
y=0;
th = 0:pi/6:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
plot(xunit, yunit);
