# Ellipse in parametric form ?

42 ビュー (過去 30 日間)
Kaleesh Bala 2018 年 7 月 26 日
コメント済み: Kaleesh Bala 2018 年 9 月 7 日
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, '-');

#### 1 件のコメント

Kaleesh Bala 2018 年 7 月 26 日
% 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

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### 回答 (1 件)

Matt J 2018 年 7 月 26 日

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;

#### 6 件のコメント

Kaleesh Bala 2018 年 9 月 6 日
I couldn't get the proper work out for this. Could you share any code regarding this case
Matt J 2018 年 9 月 6 日
I already told you that it was impossible. The foci alone aren't enough.
Kaleesh Bala 2018 年 9 月 7 日
yeah I know that ,I thought to take the surrounding rectangle boundary as tangent and then to draw an ellipse ?

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R2018a

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