# Ellipse in parametric form ?

19 views (last 30 days)
Ramesh Bala on 26 Jul 2018
Commented: Ramesh Bala on 7 Sep 2018
I'm trying to create an ellipse in parametric form. I have just two Foci along the major axis. So, how shall I get r1, r2 etc.
point1 = 10 8
point2 = 25 20
The syntax is
t = linspace(0, 2*pi, 200);
xt = r1 * cos(t) + xc;
yt = r2 * sin(t) + yc;
cot = cos(theta); sit = sin(theta);
x = xt * cot - yt * sit;
y = xt * sit - yt * cot;
plot(x, y, '-');
Ramesh Bala on 26 Jul 2018
Edited: Matt J on 26 Jul 2018
% or in other general forms :
% data
t = linspace(0,2*pi,80); % the domain of the parameter t.
x = @(t)r1.*cos(t);
y = @(t)r2.*sin(t);
figure(1)
ELLIPSE = plot(x(t),y(t));
hold off

Matt J on 26 Jul 2018
Edited: Matt J on 26 Jul 2018
You cannot determine the ellipse with only the foci. You also need to know r1. Once you know that however, you can determine r2 readily,
xc_yc=(point1+point2)/2;
c=norm(point1-xc_yc);
r2 = r1^2-c^2;
Ramesh Bala on 7 Sep 2018
yeah I know that ,I thought to take the surrounding rectangle boundary as tangent and then to draw an ellipse ?

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