# given a circle plot all possible tangents

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So as the question says I would like to obtain all the tangents to a circle.

I came across the question mentioned below

but after executing it this is what i get

The circle looks like this

enclosed are the points of the circle,its center and radius info as well as the orignal set of points on which this was drawn

the code for drawign circle is

function Circ = circle(xc,yc,R,flag)

theta=0:pi/270:2*pi;

xcircle = R*cos(theta')+xc;

ycircle = R*sin(theta')+yc;

dxda=-R.*sin(theta);

dyda=R.*cos(theta);

dydx=dyda./dxda;

if flag

plot(xcircle,ycircle);

hold on;

end

Circ=[xcircle,ycircle];

Circ=Circ';

% for i=1:size(Circ,2)

% pt=[xcircle(i) ycircle(i)];

% intcpt = pt(2) - dydx(i).*pt(1); % Calculate Intercept

% xvct = pt(1)-1:pt(1)+1; % ‘x’ Vecor For Tangent

% tngt = dydx(i).*xvct + intcpt; % Calculate Tantent

% plot(pt(1),pt(2),'gp');

% plot(xvct,tngt);

% hold on;

%

% end

end

##### 0 Comments

### Answers (1)

Geoff Hayes
on 28 Sep 2021

Sparsh - the code from https://www.mathworks.com/matlabcentral/answers/258780-how-to-plot-tangent-line-from-specified-point-to-a-circle plots the tangent for one particular point on the circle. When I run the code (provided in the answer) I do not see the first image that you included above but instead see the tangent line at a single point. If you need to show all tangents, then you would need to update the code to loop through all points on the circle and draw the tangent for each.

As for your second image, how did you generate that? I almost think there is a different question being asked here.

##### 4 Comments

Geoff Hayes
on 29 Sep 2021

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